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Astrophysics

Sun, 22 Jul 2018

Showing 332 entries from Fri, 13 Jul 2018 to Thu, 19 Jul 2018

Submitted Thu, 19 Jul 2018

[1] arXiv:1807.07557v1 [pdf, vox]

WASP-128b: a transiting brown dwarf in the dynamical-tide regime

V. Hodžić, A. H. M. J. Triaud, D. R. Anderson, F. Bouchy, A. Collier Cameron, L. Delrez, M. Gillon, C. Hellier, E. Jehin, M. Lendl, P. F. L. Maxted, F. Pepe, D. Pollacco, D. Queloz, D. Ségransan, B. Smalley, S. Udry, R. West
Submitted Thursday 19 July 2018 @ 17:55:08 GMT
7 pages, 3 figures. Submitted to MNRAS. Comments welcome

Massive companions in close orbits around G dwarfs are thought to undergo rapid orbital decay due to runaway tidal dissipation. We report here the discovery of WASP-128b, a brown dwarf discovered by the WASP survey transiting a G0V host on a $2.2\,\mathrm{d}$ orbit, where the measured stellar rotation rate places the companion in a regime where tidal interaction is dominated by dynamical tides. Under the assumption of dynamical equilibrium, we derive a value of the stellar tidal quality factor $\log{Q_\star'} = 6.96 \pm 0.19$. A combined analysis of ground-based photometry and high-resolution spectroscopy reveals a mass and radius of the host, $M_\star = 1.16 \pm 0.04\,M_\odot$, $R_\star = 1.16 \pm 0.02\,R_\odot$, and for the companion, $M_\mathrm{b} =37.5 \pm 0.8\,M_\mathrm{Jup}$​, $R_\mathrm{b} = 0.94 \pm 0.02\,R_\mathrm{Jup}​$, placing WASP-128b in the driest parts of the brown dwarf desert, and suggesting a mild inflation for its age. We estimate a remaining lifetime for WASP-128b similar to that of some ultra-short period massive hot Jupiters.

[2] arXiv:1807.05201v2 [pdf, vox]

Constraints on differential Shapiro delay between neutrinos and photons from IceCube-170922A

Sibel Boran, Shantanu Desai, Emre O. Kahya
Submitted Thursday 19 July 2018 @ 17:52:39 GMT
3 pages. Revised estimate for Shapiro delay and used delta t = 15 days to obtain bound on delta gamma

On 22nd September 2017, the IceCube Collaboration detected a neutrino with energy of about 290 TeV from the direction of the gamma-ray blazar TXS 0506+056, located at a distance of about 1.75 Gpc. During the same time, enhanced gamma-ray flaring was also simultaneously observed from multiple telescopes, giving rise to only the second coincident astrophysical neutrino/photon observation after SN 1987A. We point out that for this event, both neutrinos and photons encountered a Shapiro delay of about 6300 days along the way from the source. From this delay and the relative time difference between the neutrino and photon arrival times, one can constrain violations of Einstein's Weak Equivalence Principle (WEP) for TeV neutrinos. We constrain such violations of WEP using the Parameterized Post-Newtonian (PPN) parameter $\gamma$, and is given by $|\gamma_{\rm {\nu}}-\gamma_{\rm{E​M}}|<4.8 \times 10^{-3}$, for an arrival time difference of 15 days. This is the first direct proof that TeV neutrinos couple to gravity in the same way as photons.

[3] arXiv:1807.07548v1 [pdf, vox]

The Maximum Angular-Diameter Distance in Cosmology

Fulvio Melia, Manoj K. Yennapureddy
Submitted Thursday 19 July 2018 @ 17:34:32 GMT
10 pages, 5 figures, 2 tables. Accepted for publication in MNRAS

Unlike other observational signatures in cosmology, the angular-diameter distance d_A(z) uniquely reaches a maximum (at z_max) and then shrinks to zero towards the big bang. The location of this turning point depends sensitively on the model, but has been difficult to measure. In this paper, we estimate and use z_max inferred from quasar cores: (1) by employing a sample of 140 objects yielding a much reduced dispersion due to pre-constrained limits on their spectral index and luminosity, (2) by reconstructing d_A(z) using Gaussian processes, and (3) comparing the predictions of seven different cosmologies and showing that the measured value of z_max can effectively discriminate between them. We find that z_max=1.70 +\- 0.20---an important new probe of the Universe's geometry. The most strongly favoured model is R_h=ct, followed by Planck LCDM. Several others, including Milne, Einstein-de Sitter and Static tired light are strongly rejected. According to these results, the R_h=ct universe, which predicts z_max=1.718, has a ~92.8% probability of being the correct cosmology. For consistency, we also carry out model selection based on d_A(z) itself. This test confirms that R_h=ct and Planck LCDM are among the few models that account for angular-size data better than those that are disfavoured by z_max. The d_A(z) comparison, however, is less discerning than that with z_max, due to the additional free parameter, H_0. We find that H_0=63.4 +\- 1.2 km/s/Mpc for R_h=ct, and 69.9 +\- 1.5 km/s/Mpc for LCDM. Both are consistent with previously measured values in each model, though they differ from each other by over 4 sigma. In contrast, model selection based on z_max is independent of H_0.

[4] arXiv:1807.05611v2 [pdf, vox]

The magnetosphere structure of a Kerr black hole: marginally force-free equatorial boundary condition

Zhen Pan
Submitted Thursday 19 July 2018 @ 17:03:27 GMT

The role of equatorial boundary condition in the structure of a force-free black hole magnetosphere was rarely discussed, since previous studies have been focused on the the field lines entering the horizon. However, recent high-accuracy force-free electrodynamics (FFE) simulations \cite{East2018} show that there are both field lines entering the horizon and field lines ending up on the equatorial current sheet within the ergosphere for asymptotic uniform field configuration. For the latter field lines, the equatorial boundary condition is well approximated being marginally force-free, i.e., $B^2-E^2\approx 0$, where $B$ and $E$ are the magnetic and electric field strength, respectively. In this paper, we revisit the uniform field solution to the Kerr BH magnetosphere structure and investigate the role of the marginally force-free equatorial boundary condition. We find this boundary condition plays an important role in shaping the BH magnetosphere in various aspects, including the shape of the light surface, the near-horizon field line configuration and the source of the Poynting flux. We also propose an algorithm for numerically solving the Grad-Shafranov equation and self-consistently imposing the marginally force-free equatorial condition. As a result, we find a good agreement between our numerical solutions and the high-accuracy FFE simulations. We also discuss the applicability of the marginally force-free boundary condition and the numerical algorithm proposed in this paper for general magnetic field configurations.

[5] arXiv:1807.06668v2 [pdf, vox]

NPF: mirror development in Chile

Sebastián Zúñiga-Fernández, Amelia Bayo, Johan Olofsson, Leslie Pedrero, Claudio Lobos, Elias Rozas, Nicolás Soto, Matthias Schreiber, Pedro Escárate, Christian Romero, Hayk Hakobyan, Jorge Cuadra, Cristopher Rozas, John D. Monnier, Stefan Kraus, Mike J. Ireland, Pedro Mardones
Submitted Thursday 19 July 2018 @ 15:42:01 GMT
13 pages, SPIE Proceedings Volume 10700, Ground-based and Airborne Telescopes VII; 107003X (2018). Event: SPIE Astronomical Telescopes + Instrumentation, 2018, Austin, Texas, United States

In the era of high-angular resolution astronomical instrumentation, where long and very long baseline interferometers (constituted by many, $\sim$ 20 or more, telescopes) are expected to work not only in the millimeter and submillimeter domain, but also at near and mid infrared wavelengths (experiments such as the Planet Formation Imager, PFI, see Monnier et al. 2018 for an update on its design); any promising strategy to alleviate the costs of the individual telescopes involved needs to be explored. In a recent collaboration between engineers, experimental physicists and astronomers in Valparaiso, Chile, we are gaining expertise in the production of light carbon fiber polymer reinforced mirrors. The working principle consists in replicating a glass, or other substrate, mandrel surface with the mirrored adequate curvature, surface characteristics and general shape. Once the carbon fiber base has hardened, previous studies have shown that it can be coated (aluminum) using standard coating processes/techniques designed for glass-based mirrors. The resulting surface quality is highly dependent on the temperature and humidity control among other variables. Current efforts are focused on improving the smoothness of the resulting surfaces to meet near/mid infrared specifications, overcoming, among others, possible deteriorations derived from the replication process. In a second step, at the validation and quality control stage, the mirrors are characterized using simple/traditional tools like spherometers (down to micron precision), but also an optical bench with a Shack-Hartman wavefront sensor. This research line is developed in parallel with a more classical glass-based approach, and in both cases we are prototyping at the small scale of few tens of cms. We here present our progress on these two approaches.

[6] arXiv:1807.07496v1 [pdf, vox]

Advanced ACTPol TES Device Parameters and Noise Performance in Fielded Arrays

Kevin T. Crowley, Jason E. Austermann, Steve K. Choi, Shannon M. Duff, Patricio A. Gallardo, Shuay-Pwu Patty Ho, Johannes Hubmayr, Brian J. Koopman, Federico Nati, Michael D. Niemack, Maria Salatino, Sara M. Simon, Suzanne T. Staggs, Jason R. Stevens, Joel N. Ullom, Eve M. Vavagiakis, Edward J. Wollack
Submitted Thursday 19 July 2018 @ 15:34:39 GMT
Accepted for publication in Journal of Low Temperature Physics for LTD-17 special issue

The Advanced ACTPol (AdvACT) upgrade to the Atacama Cosmology Telescope (ACT) features arrays of aluminum manganese transition-edge sensors (TESes) optimized for ground-based observations of the Cosmic Microwave Background (CMB). Array testing shows highly responsive detectors with anticipated in-band noise performance under optical loading. We report on TES parameters measured with impedance data taken on a subset of TESes. We then compare modeled noise spectral densities to measurements. We find excess noise at frequencies around 100 Hz, nearly outside of the signal band of CMB measurements. In addition, we describe full-array noise measurements in the laboratory and in the field for two new AdvACT mid-frequency arrays, sensitive at bands centered on 90 and 150 GHz, and data for the high-frequency array (150/230 GHz) as deployed.

[7] arXiv:1807.07494v1 [pdf, vox]

Back-Reaction of Super-Hubble Cosmological Perturbations Beyond Perturbation Theory

Robert Brandenberger, Leila L. Graef, Giovanni Marozzi, Gian Paolo Vacca
Submitted Thursday 19 July 2018 @ 15:30:04 GMT
9 pages

We discuss the effect of super-Hubble cosmological fluctuations on the locally measured Hubble expansion rate. We consider a large bare cosmological constant in the early universe in the presence of scalar field matter (the dominant matter component), which would lead to a scale-invariant primordial spectrum of cosmological fluctuations. Using the leading order gradient expansion we show that the expansion rate measured by a (secondary) clock field which is not comoving with the dominant matter component obtains a negative contribution from infrared fluctuations, a contribution whose absolute value increases in time. This is the same effect which a decreasing cosmological constant would produce. This supports the conclusion that infrared fluctuations lead to a dynamical relaxation of the cosmological constant. Our analysis does not make use of any perturbative expansion in the amplitude of the inhomogeneities.

[8] arXiv:1807.07493v1 [pdf, vox]

The Carnegie RR Lyrae Program: Mid-infrared Period-Luminosity relations of RR Lyrae stars in Reticulum

Tatiana Muraveva, Alessia Garofalo, Victoria Scowcroft, Gisella Clementini, Wendy L. Freedman, Barry F. Madore, Andrew J. Monson
Submitted Thursday 19 July 2018 @ 15:29:46 GMT
17 pages, 10 figures. Accepted for publication in MNRAS

We analysed 30 RR Lyrae stars (RRLs) located in the Large Magellanic Cloud (LMC) globular cluster Reticulum that were observed in the 3.6 and 4.5 $\mu$m passbands with the Infrared Array Camera (IRAC) on board of the Spitzer Space Telescope. We derived new mid-infrared (MIR) period-luminosity PL relations. The zero points of the PL relations were estimated using the trigonometric parallaxes of five bright Milky Way (MW) RRLs measured with the Hubble Space Telescope (HST) and, as an alternative, we used the trigonometric parallaxes published in the first Gaia data release (DR1) which were obtained as part of the Tycho-Gaia Astrometric Solution (TGAS) and the parallaxes of the same stars released with the second Gaia data release (DR2). We determined the distance to Reticulum using our new MIR PL relations and found that distances calibrated on the TGAS and DR2 parallaxes are in a good agreement and, generally, smaller than distances based on the HST parallaxes, although they are still consistent within the respective errors. We conclude that Reticulum is located ~3 kpc closer to us than the barycentre of the LMC.

[9] arXiv:1807.07479v1 [pdf, vox]

Statistics of Photospheric Supergranular Cells Observed by SDO/HMI

Majedeh Noori, Mohsen Javaherian, Hossein Safari, Hamid Nadjari
Submitted Thursday 19 July 2018 @ 15:03:29 GMT
13 pages, 9 figures

Aims: The statistics of the photospheric granulation pattern are investigated using continuum images observed by Solar Dynamic Observatory (SDO)/Helioseismic and Magnetic Imager (HMI) taken at 6713~\AA. Methods: The supergranular boundaries can be extracted by tracking photospheric velocity plasma flows. The local ball-tracking method is employed to apply on the HMI data gathered over the years 2011-2015 to estimate the boundaries of the cells. The edge sharpening techniques are exerted on the output of ball-tracking to precisely identify the cells borders. To study the fractal dimensionality (FD) of supergranulation, the box counting method is used. Results: We found that both the size and eccentricity follow the log-normal distributions with peak values about 330 Mm$^2$ and 0.85, respectively. The five-year mean value of the cells number appeared in half-hour sequences is obtained to be about 60 $\pm$ 6 within an area of $350^{\prime\prime}\​times350^{\prime\pri​me}$. The cells orientation distribution presents the power-law behavior. Conclusions: The orientation of supergranular cells ($O$) and their size ($S$) follows a power-law function as $|O| \propto S^{9.5}$. We found that the non-roundish cells with smaller and larger sizes than 600 Mm$^2$ are aligned and perpendicular with the solar rotational velocity on the photosphere, respectively. The FD analysis shows that the supergranular cells form the self-similar patterns.

[10] arXiv:1807.07467v1 [pdf, vox]

Hi-5: a potential high-contrast thermal near-infrared imager for the VLTI

D. Defrère, M. Ireland, O. Absil, J. -P. Berger, W. C. Danchi, S. Ertel, A. Gallenne, F. Hénault, P. Hinz, E. Huby, S. Kraus, L. Labadie, J. -B. Le Bouquin, G. Martin, A. Matter, B. Mennesson, A. Mérand, S. Minardi, J. D. Monnier, B. Norris, G. Orban de Xivry, E. Pedretti, J. -U. Pott, M. Reggiani, E. Serabyn, J. Surdej, K. R. W. Tristram, J. Woillez
Submitted Thursday 19 July 2018 @ 14:41:16 GMT
15 pages, 3 figures, SPIE proceedings, based on arXiv:1801.04148

Hi-5 is a high-contrast (or high dynamic range) infrared imager project for the VLTI. Its main goal is to characterize young extra-solar planetary systems and exozodiacal dust around southern main-sequence stars. In this paper, we present an update of the project and key technology pathways to improve the contrast achieved by the VLTI. In particular, we discuss the possibility to use integrated optics, proven in the near-infrared, in the thermal near-infrared (L and M bands, 3-5~$\mu$m) and advanced fringe tracking strategies. We also address the strong exoplanet science case (young exoplanets, planet formation, and exozodiacal disks) offered by this wavelength regime as well as other possible science cases such as stellar physics (fundamental parameters and multiplicity) and extragalactic astrophysics (active galactic nuclei and fundamental constants). Synergies and scientific preparation for other potential future instruments such as the Planet Formation Imager are also briefly discussed.

[11] arXiv:1807.07462v1 [pdf, vox]

Mid-infrared variability of the neutrino source blazar TXS 0506$+$056

K. É. Gabányi, A. Moór, S. Frey
Submitted Thursday 19 July 2018 @ 14:33:50 GMT
3 pages, 1 figure; accepted by the Research Notes of the American Astronomical Society

The IceCube instrument detected a high-energy cosmic neutrino event on 2017 September 22 (IceCube_170922A, IceCube Collaboration 2018), which the electromagnetic follow-up campaigns associated with the flaring $\gamma$-ray blazar TXS 0506$+$056 (e.g., Padovani et al., 2018). We investigated the mid-infrared variability of the source by using the available single exposure data of the WISE satellite at $3.4$ and $4.6\mu$m. TXS 0506$+$056 experienced a $\sim 30$% brightening in both of these bands a few days prior to the neutrino event. Additional intraday infrared variability can be detected in 2010. Similar behaviour seen previously in $\gamma$-ray bright radio-loud AGN has been explained by their jet emission (e.g., Jiang et al. 2012).

[12] arXiv:1807.07459v1 [pdf, vox]

High-velocity hot CO emission close to Sgr A*: Herschel/HIFI submillimeter spectral survey toward Sgr A*

Javier R. Goicoechea, M. G. Santa-Maria, D. Teyssier, J. Cernicharo, M. Gerin, J. Pety
Submitted Thursday 19 July 2018 @ 14:22:13 GMT
Accepted for publication in A&A Letters (English not edited)

The properties of molecular gas (the fuel to form stars) inside the cavity of the circumnuclear disk (CND) are not well constrained. We present results of a velocity-resolved submillimeter (submm) scan (~480 to 1250 GHz) and of [CII]158um line observations carried out with Herschel/HIFI toward Sgr A*, and complemented with a ~2'x2' 12CO (J=3-2) map taken with the IRAM 30m telescope at ~7" resolution. We report the presence of high-positive velocity emission (up to about +300 km/s) detected in the wings of 12CO J=5-4 to 10-9 lines. This wing component is also seen in H2O (1_{1,0}-1_{0,1}) (a tracer of hot molecular gas), in [CII]158um (an unambiguous tracer of UV radiation), but not in [CI] 492,806 GHz lines. This first measurement of the high-velocity 12CO rotational ladder toward Sgr A* adds more evidence that hot molecular gas exists inside the cavity of the CND, relatively close to the super-massive black hole (< 1 pc). Observed by ALMA, this velocity range appears as a collection of 12CO (J=3-2) cloudlets (Goicoechea et al. 2018a) lying in a very harsh environment: pervaded by intense UV radiation fields, shocks, and affected by strong gravitational shears. We constrain the physical conditions of the high-positive velocity CO gas component by comparing with non-LTE excitation and radiative transfer models. We infer Tk ~400 K to 2000 K (for n_H ~ (0.2-1.0)x10^5 cm^-3). These results point toward an important role of stellar UV radiation, but we show that radiative heating alone can not explain the excitation of this ~10-60 M_Sun component of hot molecular gas inside the central cavity. Instead, strongly irradiated shocks are promising candidates.

[13] arXiv:1807.07456v1 [pdf, vox]

An atlas of cool supergiants from the Magellanic Clouds and typical interlopers: Atlas of cool supergiants in the Magellanic Clouds

Ricardo Dorda, Ignacio Negueruela, Carlos González-Fernández, Amparo Marco
Submitted Thursday 19 July 2018 @ 14:16:02 GMT
Accepted for publication in A&A. The atlas of spectra and the complete list of targets will be available at CDS, once the paper is published

We present an atlas composed of more than 1500 spectra of late-type stars (spectral types from G to M) observed simultaneously in the optical and calcium triplet spectral ranges. These spectra were obtained as part of a survey to search for cool supergiants in the Magellanic Clouds and were taken over four epochs. We provide the spectral and luminosity classification for each spectrum (71% are supergiants, 13% are giants or luminous giants, 4% are carbon or S stars, and the remaining 12% are foreground stars of lesser luminosities). We also provide a detailed guide for the spectral classification of luminous late-type stars, the result of the extensive classification work done for the atlas. Although this guide is based on classical criteria, we have put them together and re-elaborated them for modern CCD-spectra as these criteria were scattered among many different works and mainly conceived for use with photographic plate spectra. The result is a systematic, well-tested process for identifying and classifying luminous late-type stars, illustrated with CCD spectra of standard stars and the classifications of our own catalogue.

[14] arXiv:1807.07451v1 [pdf, vox]

$H_0$ tension and the de Sitter Swampland

Eoin Ó Colgáin, Maurice H. P. M. van Putten, Hossein Yavartanoo
Submitted Thursday 19 July 2018 @ 14:09:51 GMT
4 pages, comments welcome

Local measurements of the Hubble constant $H_0$ are at odds with $\Lambda$CDM analysis of Planck data and this tension is increasing. This suggests the presence of potentially new physics beyond $\Lambda$CDM. Recently, it has been conjectured that de Sitter vacua inhabit the Swampland of inconsistent low-energy effective theories coupled to gravity. Viewing this proposal through the prism of data, we abandon the notion of stable de Sitter vacua, which allows us to alleviate the $H_0$ tension, but at the cost of violating the Swampland criteria.

[15] arXiv:1807.07402v1 [pdf, vox]

The MICADO first light imager for ELT: its astrometric performance

J. -U. Pott, G. Rodeghiero, H. Riechert, D. Massari, M. Fabricius, C. Arcidiacono, R. I. Davies
Submitted Thursday 19 July 2018 @ 13:35:49 GMT
5 pages, submitted to SPIE 2018 Astronomical Telescopes + Instrumentation

We report on our ongoing efforts to ensure that the MICADO NIR imager reaches differential absolute (often abbreviated: relative) astrometric performance limited by the SNR of typical observations. The exceptional 39m diameter collecting area in combination with a powerful multi-conjugate adaptive optics system (called MAORY) brings the nominal centroiding error, which scales as FWHM/SNR, down to a few 10 uas. Here we show that an exceptional effort is needed to provide a system which delivers adequate and calibrateable astrometric performance over the full field of view (up to 53 arcsec diameter).

[16] arXiv:1807.07375v1 [pdf, vox]

The $γ$-ray spectrum of the core of Centaurus A as observed with H.E.S.S. and Fermi-LAT

H. E. S. S. Collaboration, H. Abdalla, A. Abramowski, F. Aharonian, F. Ait Benkhali, E. O. Angüner, M. Arakawa, C. Armand, M. Arrieta, M. Backes, A. Balzer, M. Barnard, Y. Becherini, J. Becker Tjus, D. Berge, S. Bernhard, K. Bernlöhr, R. Blackwell, M. Böttcher, C. Boisson, J. Bolmont, S. Bonnefoy, P. Bordas, J. Bregeon, F. Brun, P. Brun, M. Bryan, M. Büchele, T. Bulik, M. Capasso, S. Caroff, A. Carosi, S. Casanova, M. Cerruti, N. Chakraborty, R. C. G. Chaves, A. Chen, J. Chevalier, S. Colafrancesco, B. Condon, J. Conrad, I. D. Davids, J. Decock, C. Deil, J. Devin, P. deWilt, L. Dirson, A. Djannati-Ataï, A. Donath, L. O'C. Drury, J. Dyks, T. Edwards, K. Egberts, G. Emery, J. -P. Ernenwein, S. Eschbach, C. Farnier, S. Fegan, M. V. Fernandes, A. Fiasson, G. Fontaine, S. Funk, M. Füßling, S. Gabici, Y. A. Gallant, T. Garrigoux, F. Gaté, G. Giavitto, D. Glawion, J. F. Glicenstein, D. Gottschall, M. -H. Grondin, J. Hahn, M. Haupt, J. Hawkes, G. Heinzelmann, G. Henri, G. Hermann, J. A. Hinton, W. Hofmann, C. Hoischen, T. L. Holch, M. Holler, D. Horns, A. Ivascenko, H. Iwasaki, A. Jacholkowska, M. Jamrozy, D. Jankowsky, F. Jankowsky, M. Jingo, L. Jouvin, I. Jung-Richardt, M. A. Kastendieck, K. Katarzyński, M. Katsuragawa, U. Katz, D. Kerszberg, D. Khangulyan, B. Khélifi, J. King, S. Klepser, D. Klochkov, W. Kluźniak, Nu. Komin, K. Kosack, S. Krakau, M. Kraus, P. P. Krüger, H. Laffon, G. Lamanna, J. Lau, J. Lefaucheur, A. Lemière, M. Lemoine-Goumard, J. -P. Lenain, E. Leser, T. Lohse, M. Lorentz, R. Liu, R. López-Coto, I. Lypova, D. Malyshev, V. Marandon, A. Marcowith, C. Mariaud, R. Marx, G. Maurin, N. Maxted, M. Mayer, P. J. Meintjes, M. Meyer, A. M. W. Mitchell, R. Moderski, M. Mohamed, L. Mohrmann, K. Morå, E. Moulin, T. Murach, S. Nakashima, M. de Naurois, H. Ndiyavala, F. Niederwanger, J. Niemiec, L. Oakes, P. O'Brien, H. Odaka, S. Ohm, M. Ostrowski, I. Oya, M. Padovani, M. Panter, R. D. Parsons, N. W. Pekeur, G. Pelletier, C. Perennes, P. -O. Petrucci, B. Peyaud, Q. Piel, S. Pita, V. Poireau, D. A. Prokhorov, H. Prokoph, G. Pühlhofer, M. Punch, A. Quirrenbach, S. Raab, R. Rauth, A. Reimer, O. Reimer, M. Renaud, R. de los Reyes, F. Rieger, L. Rinchiuso, C. Romoli, G. Rowell, B. Rudak, C. B. Rulten, V. Sahakian, S. Saito, D. A. Sanchez, A. Santangelo, M. Sasaki, R. Schlickeiser, F. Schüssler, A. Schulz, U. Schwanke, S. Schwemmer, M. Seglar-Arroyo, A. S. Seyffert, N. Shafi, I. Shilon, K. Shiningayamwe. R. Simoni, H. Sol, F. Spanier, M. Spir-Jacob, Ł. Stawarz, R. Steenkamp, C. Stegmann, C. Steppa, I. Sushch, T. Takahashi, J. -P. Tavernet, T. Tavernier, A. M. Taylor, R. Terrier, L. Tibaldo, D. Tiziani, M. Tluczykont, C. Trichard, M. Tsirou, N. Tsuji, R. Tuffs, Y. Uchiyama, D. J. van der Walt, C. van Eldik, C. van Rensburg, B. van Soelen, G. Vasileiadis, J. Veh, C. Venter, A. Viana, P. Vincent, J. Vink, F. Voisin, H. J. Völk, T. Vuillaume, Z. Wadiasingh, S. J. Wagner, P. Wagner, R. M. Wagner, R. White, A. Wierzcholska, P. Willmann, A. Wörnlein, D. Wouters, R. Yang, D. Zaborov, M. Zacharias, R. Zanin, A. A. Zdziarski, A. Zech, F. Zefi, A. Ziegler, J. Zorn, N. Żywucka, Fermi-LAT collaboration, J. D. Magill, S. Buson, C. C. Cheung, J. S. Perkins, Y. Tanaka
Submitted Thursday 19 July 2018 @ 12:54:51 GMT
Accepted for publication in A&A, Abstract abridged for arXiv submission

Centaurus A (Cen A) is the nearest radio galaxy discovered as a very-high-energy (VHE; 100 GeV-100 TeV) $\gamma$-ray source by the High Energy Stereoscopic System (H.E.S.S.). It is a faint VHE $\gamma$-ray emitter, though its VHE flux exceeds both the extrapolation from early Fermi-LAT observations as well as expectations from a (misaligned) single-zone synchrotron-self Compton (SSC) description. The latter satisfactorily reproduces the emission from Cen A at lower energies up to a few GeV. New observations with H.E.S.S., comparable in exposure time to those previously reported, were performed and eight years of Fermi-LAT data were accumulated to clarify the spectral characteristics of the $\gamma$-ray emission from the core of Cen A. The results allow us for the first time to achieve the goal of constructing a representative, contemporaneous $\gamma$-ray core spectrum of Cen A over almost five orders of magnitude in energy. Advanced analysis methods, including the template fitting method, allow detection in the VHE range of the core with a statistical significance of 12$\sigma$ on the basis of 213 hours of total exposure time. The spectrum in the energy range of 250 GeV-6 TeV is compatible with a power-law function with a photon index $\Gamma=2.52\pm0.13_​{\mathrm{stat}}\pm0.​20_{\mathrm{sys}}$. An updated Fermi-LAT analysis provides evidence for spectral hardening by $\Delta\Gamma\simeq0​.4\pm0.1$ at $\gamma$-ray energies above $2.8^{+1.0}_{-0.6}$ GeV at a level of $4.0\sigma$. The fact that the spectrum hardens at GeV energies and extends into the VHE regime disfavour a single-zone SSC interpretation for the overall spectral energy distribution (SED) of the core and is suggestive of a new $\gamma$-ray emitting component connecting the high-energy emission above the break energy to the one observed at VHE energies.

[17] arXiv:1807.07359v1 [pdf, vox]

UVIT imaging of WLM : Demographics of star forming regions in the nearby dwarf irregular galaxy

Chayan Mondal, Annapurni Subramaniam, Koshy George
Submitted Thursday 19 July 2018 @ 12:13:23 GMT
Accepted for publication in AJ

We present a study of star forming regions and its demographics in the nearby dwarf irregular galaxy WLM using the Ultra-Violet Imaging Telescope (UVIT) multi band observations in three filters F148W, N245M and N263M. We find that the UV emission is extended at least up to 1.7 kpc, with the NUV emission more extended than the FUV. We create UV color maps ((F148W$-$N245M) and (F148W$-$N263M)) to study the temperature morphology of young stellar complexes with the help of theoretical models. We identify several complexes with temperature T $>$ 17500 K which are likely to be the OB associations present in the galaxy. These complexes show good spatial correlation with the H$\alpha$ emitting regions, H$~$I distribution and HST detected hot stars. The hot star forming regions are found to be clumpy in nature and show a hierarchical structure, with sizes in the range of 4 - 50 pc, with a large number with sizes $<$ 10 pc. The south western part of the galaxy shows many hot star forming regions, high level of H$\alpha$ emission and low column density of H$~$I which altogether denote a vigorous recent star formation. WLM is likely to have a large fraction of low mass compact star forming regions with mass M $< 10^3 M_{\odot}$, in agreement with the size and mass of the CO clouds. We estimate the star formation rate of WLM to be $\sim$ 0.008 $M_{\odot}/yr$, which is similar to the average value measured for nearby dwarf irregular galaxies.

[18] arXiv:1807.06232v2 [pdf, vox]

FOREST Unbiased Galactic Plane Imaging Survey with the Nobeyama 45-m Telescope (FUGIN) IV: Galactic Shock Wave and Molecular Bow Shock in the 4-kpc Arm of the Galaxy

Y. Sofue, M. Kohno, K. Torii, T. Umemoto, N. Kuno, K. Tachihara, T. Minamidani, S. Fujita, M. Matsuo, A. Nishimura, Y. Tsuda, M. Seta
Submitted Thursday 19 July 2018 @ 11:44:06 GMT
13 pages, 11 figures, 1 table, PASJ in press (2019 special issue for NRO-45m Telescope FOREST project)

The FUGIN CO survey with the Nobeyama 45-m Telescope revealed the 3D structure of a galactic shock wave in the tangential direction of the 4-kpc molecular arm. The shock front is located at G30.5+00.0+95 km/s on the up-stream (lower longitude) side of the star-forming complex W43 (G30.8-0.03), and composes a molecular bow shock (MBS) concave to W43, exhibiting an arc-shaped molecular ridge perpendicular to the galactic plane with width $\sim 0^\circ.1$ (10 pc) and vertical length $\sim 1^\circ \ (100\ {\rm pc})$. The MBS is coincident with the radio continuum bow of thermal origin, indicating association of ionized gas and similarity to a cometary bright-rimmed cloud. The up-stream edge of the bow is sharp with a growth width of $\sim 0.5$ pc indicative of shock front property. The velocity width is $\sim 10$ km/s, and the center velocity decreases by $\sim 15$ \kms from bottom to top of the bow. The total mass of molecular gas in MBS is estimated to be $\sim 1.2\times 10^6 <_\odot$ and ionized gas $\sim 2\times 10^4 M_\odot$. The vertical disk thickness increases step like at the MBS by $\sim 2$ times from lower to upper longitude, which indicates hydraulic-jump in the gaseous disk. We argue that the MBS was formed by the galactic shock compression of an accelerated flow in the spiral-arm potential encountering the W43 molecular complex. A bow-shock theory can well reproduce the bow morphology. We argue that molecular bows are common in galactic shock waves not only in the Galaxy but also in galaxies, where MBS are associated with giant cometary HII regions. We also analyzed the HI data in the same region to obtain a map of HI optical depth and molecular fraction. We found a firm evidence of HI-to-H$_{2}$ transition in the galactic shock as revealed by a sharp molecular front at the MBS front.

[19] arXiv:1807.07334v1 [pdf, vox]

Giant burst of methanol maser in S255IR-NIRS3

Marian Szymczak, Mateusz Olech, Paweł Wolak, Eric Gérard, Anna Bartkiewicz
Submitted Thursday 19 July 2018 @ 10:33:24 GMT
9 pages, 9 figures

Context: High-mass young stellar objects (HMYSOs) can undergo accretion episodes that strongly affect the star evolution, the dynamics of the disk, and its chemical evolution. Recently reported extraordinary bursts in the methanol maser emission may be the observational signature of accretion events in deeply embedded HMYSOs. Aims: We analyze the light curve of 6.7 GHz methanol masers in S255IR-NIRS3 during the 2015-2016 burst. Methods: 8.5-year monitoring data with an average sampling interval of 5 days were obtained with the Torun 32 m radio telescope. Archival data were added, extending the time series to ~27 years. Results: The maser emission showed moderate (25-30%) variability on timescales of months to years over ~23 years since its discovery. The main burst was preceded by a one-year increase of the total flux density by a factor of 2.5, then it grew by a factor of 10 over ~0.4 years and declined by a factor of 8 during the consecutive 2.4 years. The peak maser luminosity was a factor of 24.5 higher than the pre-burst quiescent value. The light curves of individual features showed considerable diversity but indicated a general trend of suppression of the maser emission at blueshifted (<4.7 km s$^{-1}$) velocities when the redshifted emission rapidly grew and new emission features appeared at velocities >5.8 km s$^{-1}$. This new emission provided a contribution of about 80% to the maser luminosity around the peak of the burst. Conclusions: The onset of the maser burst exactly coincides with that of the infrared burst estimated from the motion of the light echo. This strongly supports the radiative pumping scheme of the maser transition. The growth of the maser luminosity is the result of an increasing volume of gas where the maser inversion is achieved.

[20] arXiv:1807.07324v1 [pdf, vox]

Foreground Biases on Primordial Non-Gaussianity Measurements from the CMB Temperature Bispectrum: Implications for Planck and Beyond

J. Colin Hill
Submitted Thursday 19 July 2018 @ 10:01:45 GMT
18 pages, 10 figures, abstract slightly abridged, comments welcome

The cosmic microwave background (CMB) temperature bispectrum is currently the most precise tool for constraining primordial non-Gaussianity (NG). The Planck temperature data tightly constrain the amplitude of local-type NG: $f_{\rm NL}^{\rm loc} = 2.5 \pm 5.7$. Here, we compute previously-neglected foreground biases in temperature-based $f_{\rm NL}^{\rm loc}$ measurements. We consider the integrated Sachs-Wolfe (ISW) effect, gravitational lensing, the thermal (tSZ) and kinematic Sunyaev-Zel'dovich (kSZ) effects, and the cosmic infrared background (CIB). In standard analyses, a significant foreground bias arising from the ISW-lensing bispectrum is subtracted from the $f_{\rm NL}^{\rm loc}$ measurement. However, many other terms sourced by the ISW, lensing, tSZ, kSZ, and CIB fields are also present in the temperature bispectrum. We compute the dominant biases on $f_{\rm NL}^{\rm loc}$ arising from these signals. Most of the biases are non-blackbody, and are thus reduced by multifrequency component separation methods; however, recent analyses have found that extragalactic foregrounds are present at non-negligible levels in the Planck component-separated maps. Moreover, the Planck FFP8 simulations do not include the correlations amongst components that are responsible for these biases. We compute the biases for individual frequencies, finding that some are comparable to the statistical error bar on $f_{\rm NL}^{\rm loc}$, even for the main CMB channels (100, 143, and 217 GHz). For future experiments, they can greatly exceed the statistical error bar (considering temperature only). A full assessment will require calculations in tandem with component separation, ideally using simulations. Similar biases will also afflict measurements of equilateral and orthogonal NG, as well as trispectrum NG. We conclude that the search for primordial NG using Planck data may not yet be over.

[21] arXiv:1807.07294v1 [pdf, vox]

The variability of the warm absorber in I Zwicky 1 as seen by XMM-Newton

C. V. Silva, E. Costantini, M. Giustini, G. A. Kriss, W. N. Brandt, L. C. Gallo, D. R. Wilkins
Submitted Thursday 19 July 2018 @ 08:52:04 GMT
10 pages, 7 figures. Accepted for publication in MNRAS

We present new XMM-Newton observations of the intriguing warm absorber in I Zwicky 1. This luminous and nearby narrow-line Seyfert 1 galaxy shows ionized absorption by two components of outflowing gas; a low and a high-ionization phase with log $\xi$~0 and log $\xi$~2 respectively. Detailed modelling of these data reveal a complex and variable multi-phase warm absorber. However, we find the changes in the ionization state of the gas not to be straightforwardly correlated with the variability of the intrinsic continuum source, in apparent contrast with photoionization equilibrium. The observed variability hints instead at a close connection between the two gas components, possibly both directly connected to the accretion disc activity. We thus suggest a phenomenological model capable of explaining these observations, consisting of a clumpy outflow where the high and the low-ionization components are closely linked. Changes in ionization over the years are mainly driven by the different densities of the clumps crossing the observer's line-of-sight, in which the `skin' layer facing the source accounts for the more ionized component.

[22] arXiv:1807.07287v1 [pdf, vox]

Probing modified gravity in cosmic filaments

Alex Ho, Max Gronke, Bridget Falck, David F. Mota
Submitted Thursday 19 July 2018 @ 08:31:34 GMT
11 pages, 17 figures, submitted to A&A

Multiple modifications of general relativity (GR) have been proposed in the literature in order to understand the nature of the accelerated expansion of the Universe. However, thus far all the predictions of GR have been confirmed with constantly increasing accuracy. In this work, we study the imprints of a particular class of models -- `screened' modified gravity theories -- on cosmic filaments. We utilize the $N$-body code ISIS/RAMSES to simulate the symmetron model and the Hu-Sawicky $f(R)$ model, and we post-process the output with DisPerSE to identify the filaments of the cosmic web. We investigate how the global properties of the filaments -- such as their lengths, masses, and thicknesses -- as well as their radial density and speed profiles change under different gravity theories. We find that filaments are, on average, shorter and denser in modified gravity models compared to in $\Lambda$CDM. We also find that the speed profiles of the filaments are enhanced, consistent with theoretical expectations. Overall, our results suggest that cosmic filaments can be an effective complementary probe of screened modified gravity theories on Mpc scales.

[23] arXiv:1807.07280v1 [pdf, vox]

The duty cycle of the radio galaxy B2 0258+35

M. Brienza, R. Morganti, M. Murgia, N. Vilchez, B. Adebahr, E. Carretti, R. Concu, F. Govoni, J. Harwood, H. Intema, F. Loi, A. Melis, R. Paladino, S. Poppi, A. Shulevski, V. Vacca, G. Valente
Submitted Thursday 19 July 2018 @ 08:15:36 GMT
13 pages, 4 figures, 6 tables, A&A accepted

Radio loud Active Galactic Nuclei are episodic in nature, cycling through periods of activity and quiescence. In this work we investigate the duty cycle of the radio galaxy B2~0258+35, which was previously suggested to be a restarted radio galaxy based on its morphology. The radio source consists of a pair of kpc-scale jets embedded in two large-scale lobes (~240 kpc) with relaxed shape and very low surface brightness, which resemble remnants of a past AGN activity. We combine new LOFAR data at 145 MHz and new SRT data at 6600 MHz with available WSRT data at 1400 MHz to investigate the spectral properties of the outer lobes and derive their age. Interestingly, the spectrum of both the outer Northern and Southern lobes is not ultra-steep as expected for an old ageing plasma with spectral index values equal to $\rm \alpha_{1400}^{145}=​0.48\pm0.11$ and $\rm \alpha_{6600}^{1400}​=0.69\pm0.20$ in the outer Northern lobe, and $\rm \alpha_{1400}^{145}=​0.73\pm0.07$ in the outer Southern lobe. Moreover, despite the wide frequency coverage available for the outer Northern lobe (145-6600~MHz), we do not identify a significant spectral curvature (SPC$\simeq$0.2$\pm0​.2$). While mechanisms such as in-situ particle reacceleration, mixing or compression can temporarily play a role in preventing the spectrum from steepening, in no case seem the outer lobes to be compatible with being very old remnants of past activity as previously suggested (with age $\gtrsim$ 80 Myr). We conclude that either the large-scale lobes are still fuelled by the nuclear engine or the jets have switched off no more than a few tens of Myr ago. Our study shows the importance of combining morphological and spectral properties to reliably classify the evolutionary stage of low surface brightness, diffuse emission that low frequency observations are revealing around a growing number of radio sources.

[24] arXiv:1807.07274v1 [pdf, vox]

Finding closure: approximating Vlasov-Poisson using finitely generated cumulants

Cora Uhlemann
Submitted Thursday 19 July 2018 @ 07:50:53 GMT
17 pages, 1 figure

Since dark matter almost exclusively interacts gravitationally, the phase-space dynamics is described by the Vlasov-Poisson equation. A key characteristic is its infinite cumulant hierarchy, a tower of coupled evolution equations for the cumulants of the phase-space distribution. While on large scales the matter distribution is well described as a fluid and the hierarchy can be truncated, smaller scales are in the multi-stream regime in which all higher-order cumulants are sourced through nonlinear gravitational collapse. This regime is crucial for the formation of bound structures and the emergence of characteristic properties such as their density profiles. We present a novel closure strategy for the cumulant hierarchy that is inspired by finitely generated cumulants and hence beyond truncation. This constitutes a constructive approach for reducing nonlinear phase-space dynamics of Vlasov-Poisson to a closed system of equations in position space. Using this idea, we derive Schr\"odinger-Poisso​n as approximate quantal method for solving classical dynamics of Vlasov-Poisson with cold initial conditions. Our deduction complements the common reverse inference of the Schr\"odinger-Vlasov relation using a semi-classical limit of quantum dynamics and provides a clearer picture of the correspondence between classical and quantal dynamics. Our framework outlines an essential first step towards constructing approximate methods for Vlasov-like systems in cosmology and plasma physics with different initial conditions and potentials.

[25] arXiv:1807.07272v1 [pdf, vox]

High-resolution observations of the symbiotic system R Aqr. Direct imaging of the gravitational effects of the secondary on the stellar wind

V. Bujarrabal, J. Alcolea, J. Mikolajewska, A. Castro-Carrizo, S. Ramstedt
Submitted Thursday 19 July 2018 @ 07:47:42 GMT
Accepted by Astronomy & Astrophysics. 7 pages, 6 figures

We have observed the symbiotic stellar system R Aqr, aiming to describe the gravitational interaction between the white dwarf (WD) and the wind from the Mira star, the key phenomenon driving the symbiotic activity and the formation of nebulae in such systems. We present high-resolution ALMA maps of the 12CO and 13CO J=3-2 lines, the 0.9 mm continuum distribution, and some high-excitation molecular lines in R Aqr. The maps, which have resolutions ranging between 40 milliarcsecond (mas) and less than 20 mas, probe the circumstellar regions at suborbital scales as the distance between the stars is ~ 40 mas. Our observations show the gravitational effects of the secondary on the stellar wind. The AGB star was identified in our maps from the continuum and molecular line data, and we estimated the probable position of the secondary from a new estimation of the orbital parameters. The (preliminary) comparison of our maps with theoretical predictions is surprisingly satisfactory and the main expected gravitational effects are directly mapped for the first time. We find a strong focusing in the equatorial plane of the resulting wind, which shows two plumes in opposite directions that have different velocities and very probably correspond to the expected double spiral due to the interaction. Our continuum maps show the very inner regions of the nascent bipolar jets, at scales of some AU. Continuum maps obtained with the highest resolution show the presence of a clump that very probably corresponds to the emission of the ionized surroundings of the WD and of a bridge of material joining both stars, which is likely material flowing from the AGB primary to the accretion disk around the WD secondary.

[26] arXiv:1807.07269v1 [pdf, vox]

The metal-rich halo component extended in z: a characterization with Gaia DR2 and APOGEE

Emma Fernández-Alvar, J. G. Fernández-Trincado, Edmundo Moreno, William J. Schuster, Leticia Carigi, Alejandra Recio-Blanco, Timothy C. Beers, Cristina Chiappini, Friedrich Anders, Basílio X. Santiago, Anna B. A. Queiroz, Ángeles Pérez-Villegas, Olga Zamora, D. A. García-Hernández
Submitted Thursday 19 July 2018 @ 07:38:32 GMT
16 pages, 12 figures, paper submitted to MNRAS

We report an analysis of the metal-rich tail ([Fe/H] $> -0.75$) of halo stars located at distances from the Galactic plane $z$ up to $|z| \sim 10$ kpc, observed by the Apache Point Observatory Galactic Evolution Experiment (APOGEE). We examine the chemistry, kinematics, and dynamics of this metal-rich halo sample using chemical abundances and radial velocities provided by the fourteenth APOGEE data release (DR14) and proper motions from the second Gaia data release (DR2). The analysis reveals three chemically different stellar populations in the [Mg/Fe] vs. [Fe/H] space -- the two distinct halo populations already reported in the literature, and a third group with intermediate [Mg/Fe] $\sim$+0.1. We derive the $U$, $V$ and $W$ velocity components with respect to the Local Standard of Rest, as well as orbits for the three stellar groups, and find that they differ also in their kinematical and dynamical properties. The high-[Mg/Fe] population exhibits a mean prograde rotation, as well as orbits that are more bound and closer to the plane, whereas the low-[Mg/Fe] population has $<V>$ closer to 0, and stars that move in less-bound orbits reaching larger distances from the centre and the Galactic plane. The intermediate-Mg stars exhibit different orbital characteristics, moving with a strong prograde rotation and low excentricity, but in less-bound orbits. This stellar population resembles the two stellar overdensities lying about $|z| \sim 5$ kpc recently reported in the literature, for which a disc origin has been claimed.

[27] arXiv:1807.06594v2 [pdf, vox]

A 100-pc Scale, Fast and Dense Outflow in Narrow-Line Seyfert 1 Galaxy IRAS04576+0912

Toshihiro Kawaguchi, Shinobu Ozaki, Hajime Sugai, Kazuya Matsubayashi, Takashi Hattori, Atsushi Shimono, Kentaro Aoki, Yutaka Hayano, Yosuke Minowa, Kazuma Mitsuda, Yasuhito Hashiba
Submitted Thursday 19 July 2018 @ 07:35:28 GMT
7 pages, 2 figures, Accepted for publication in PASJ

We report the initial result of an adaptive-optics assisted, optical integral-field-unit observation on IRAS04576+0912, the nearest (z=0.039) active galactic nucleus with a prominent blueshift/tail in [O III] emission from a sample of such objects that we have collected from the literature. We aim at addressing the putative quasar-mode feedback process with Subaru/Kyoto 3D II+AO188. The optical waveband (6400--7500 AA) enables us to measure the gas density via the [S II] doublets, in contrast to earlier Near-IR studies. Since the fast [O III] outflow happens only around rapidly growing central black holes, this object is suitable for investigating the black hole-galaxy coevolution. The obtained data cube exhibits blue tail in the [S II] emission at many lenslets. By fitting the spectrum with the high excess flux at the [S II] blue tail, we find the fast (~ 860 km/s), dense (>3000/cc), wide-angle and offset outflow in central 100-pc scales. Although the large opening angle and the high gas outflow-to-accretion ratio may favour the feedback hypothesis, the inferred kinetic power injection rate of this ionized gas outflow seems insufficient to influence the whole host galaxy. A conventional assumption of a low density must have overestimated the feedback process.

[28] arXiv:1807.07252v1 [pdf, vox]

Exploring the Nature of the 2016 γ-ray Emission in the Blazar 1749+096

Dae-Won Kim, Sascha Trippe, Sang-Sung Lee, Jae-Young Kim, Juan-Carlos Algaba, Jeffrey Hodgson, Jongho Park, Motoki Kino, Guang-Yao Zhao, Kiyoaki Wajima, Jee Won Lee, Sincheol Kang
Submitted Thursday 19 July 2018 @ 06:24:45 GMT
11 pages, 7 figures, 2 tables. To appear in MNRAS (submitted: 2018 May 9; accepted: 2018 July 15)

Recent Fermi-Large Area Telescope (LAT) light curves indicate an active $\gamma$-ray state spanning about five months from 2016 June to 2016 October in the BL Lac object 1749+096 (OT 081). During this period, we find two notable $\gamma$-ray events: an exceptionally strong outburst followed by a significant enhancement (local peak). In this study, we analyze multi-waveband light curves (radio, optical, X-ray, and $\gamma$-ray) plus very-long baseline interferometry (VLBI) data to investigate the nature of the $\gamma$-ray events. The $\gamma$-ray outburst coincides with flux maxima at longer wavelengths. We find a spectral hardening of the $\gamma$-ray photon index during the $\gamma$-ray outburst. The photon index shows a transition from a softer-when-brighter to a harder-when-brighter trend at around 1.8 $\times$ $10^{-7}$ ph cm$^{-2}$ s$^{-1}$. We see indication that both the $\gamma$-ray outburst and the subsequent enhancement precede the propagation of a polarized knot in a region near the VLBI core. The highest polarized intensity, 230\,mJy, and an electric vector position angle rotation, by $\sim$32$^{\circ}$, are detected about 12 days after the $\gamma$-ray outburst. We conclude that both $\gamma$-ray events are caused by the propagation of a disturbance in the mm-wave core.

[29] arXiv:1807.07251v1 [pdf, vox]

ASASSN-14dq: A fast-declining type II-P Supernova in a low-luminosity host galaxy

Avinash Singh, S. Srivastav, Brajesh Kumar, G. C. Anupama, D. K. Sahu
Submitted Thursday 19 July 2018 @ 06:19:27 GMT
28 pages, 29 figures, Accepted in MNRAS

Optical broadband (UBVRI) photometric and low-resolution spectroscopic observations of the type II-P supernova (SN) ASASSN-14dq are presented. ASASSN-14dq exploded in a low-luminosity/metal​licity host galaxy UGC 11860, the signatures of which are present as weak iron lines in the photospheric phase spectra. The SN has a plateau duration of $\sim\,$90 d, with a plateau decline rate of 1.38 $\rm mag\ (100 d)^{-1}$ in V-band which is higher than most type II-P SNe. ASASSN-14dq is a luminous type II-P SN with a peak $V$-band absolute magnitude of -17.7$\,\pm\,$0.2 mag. The light curve of ASASSN-14dq indicates it to be a fast-declining type II-P SN, making it a transitional event between the type II-P and II-L SNe. The empirical relation between the steepness parameter and $\rm ^{56}Ni$ mass for type II SNe was rebuilt with the help of well-sampled light curves from the literature. A $\rm ^{56}Ni$ mass of $\sim\,$0.029 M$_{\odot}$ was estimated for ASASSN-14dq, which is slightly lower than the expected $\rm ^{56}Ni$ mass for a luminous type II-P SN. Using analytical light curve modelling, a progenitor radius of $\rm \sim3.6\times10^{13}​$ cm, an ejecta mass of $\rm \sim10\ M_{\odot}$ and a total energy of $\rm \sim\,1.8\times 10^{51}$ ergs was estimated for this event. The photospheric velocity evolution of ASASSN-14dq resembles a type II-P SN, but the Balmer features (H$\alpha$ and H$\beta$) show relatively slow velocity evolution. The high-velocity H$\alpha$ feature in the plateau phase, the asymmetric H$\alpha$ emission line profile in the nebular phase and the inferred outburst parameters indicate an interaction of the SN ejecta with the circumstellar material (CSM).

[30] arXiv:1807.07245v1 [pdf, vox]

Young radio jets breaking free: molecular and HI outflows in their centers

Raffaella Morganti, Tom Oosterloo, Robert Schulz, Clive Tadhunter, J. B. Raymond Oonk
Submitted Thursday 19 July 2018 @ 05:41:11 GMT
Proceedings of IAU-S342 -- Perseus in Sicily: from black hole to cluster outskirts -- K. Asada, E. de Gouveia dal Pino, H. Nagai, R. Nemmen, M. Giroletti, eds - 6 pages, 3 figures

Our view of the central regions of AGN has been enriched by the discovery of fast and massive outflows of HI and molecular gas. Here we present a brief summary of results obtained for young (and restarted) radio AGN. We find that HI outflows tend to be particularly common in this group of objects. This supports the idea that the jet, expanding in a clumpy medium, plays a major role in driving these outflows. The clumpiness of the medium is confirmed by VLBI and ALMA observations. The HI observations reveal that, at least part of the gas, is distributed in clouds with sizes up to a few tens of pc and mass ~10^4 Msun. A change of the conditions in the outflow, with an increasing fraction of diffuse components, as the radio jets grow, is suggested by the high resolution HI observations. The molecular gas completes the picture, showing that the radio plasma jet can couple well with the ISM, strongly affecting the kinematics, but also the physical conditions of the molecular gas. This is confirmed by numerical simulations reproducing, to first order, the kinematics of the gas.

[31] arXiv:1807.07234v1 [pdf, vox]

Probing gravitational wave polarizations with Advanced LIGO, Advanced Virgo and KAGRA

Yuki Hagihara, Naoya Era, Daisuke Iikawa, Hideki Asada
Submitted Thursday 19 July 2018 @ 04:11:43 GMT
14 pages, 4 figures

Assuming that, for a given source of gravitational waves (GWs), we know its sky position, as a case of GW events with an electromagnetic counterpart such as GW170817, we discuss a null stream method to probe GW polarizations including spin-0 (scalar) GW modes and spin-1 (vector) modes, especially with an expected network of Advanced LIGO, Advanced Virgo and KAGRA. For two independent null streams for four unaligned GW detectors, we study a location on the sky, exactly at which the spin-0 modes of GWs vanish in any null stream for the GW detector network, though the strain output at a detector may contain the spin-0 modes. Our numerical calculations show that there exist seventy-two sky positions that satisfy this condition of killing the spin-0 modes in the null streams. If a GW source with an electromagnetic counterpart is found in one of the seventy-two sky positions, the spin-1 modes will be testable separately from the spin-0 modes by the null stream method. In addition, we study a superposition of the two null streams to show that any one of the three modes (one combined spin-0 and two spin-1 modes) can be eliminated by suitably adjusting a weighted superposition of the null streams and thereby a set of the remaining polarization modes can be experimentally tested.

[32] arXiv:1807.07221v1 [pdf, vox]

Direct detection of mirror helium dark matter in the CRESST-III experiment

R. Foot
Submitted Thursday 19 July 2018 @ 02:34:16 GMT
5 pages

Within the context of mirror dark matter, the dominant mass component of the Milky Way dark halo consists of mirror helium ions. Mirror helium can interact with ordinary matter if the kinetic mixing interaction exists. Mirror helium being rather light, $m \simeq 3.73$ GeV, generally produces sub-keV recoils in direct detection experiments. Recently, the CRESST-III experiment has began probing the sub-keV recoil energy region and is currently the most sensitive probe of such particles. We point out here that the small excess seen in the low energy recoil data obtained in the CRESST-III experiment is consistent with mirror helium scattering if the kinetic mixing parameter is around $\epsilon \approx 5 \times 10^{-10}$. This kinetic mixing strength lies within the estimated range favoured by small scale structure considerations.

[33] arXiv:1807.06761v2 [pdf, vox]

Characterization of microdot apodizers for imaging exoplanets with next-generation space telescopes

Manxuan Zhang, Garreth Ruane, Jacques-Robert Delorme, Dimitri Mawet, Nemanja Jovanavic, Jeffrey Jewell, Stuart Shaklan, J. Kent Wallace
Submitted Thursday 19 July 2018 @ 02:27:37 GMT
Space Telescopes and Instrumentation 2018: Optical, Infrared, and Millimeter Wave

A major science goal of future, large-aperture, optical space telescopes is to directly image and spectroscopically analyze reflected light from potentially habitable exoplanets. To accomplish this, the optical system must suppress diffracted light from the star to reveal point sources approximately ten orders of magnitude fainter than the host star at small angular separation. Coronagraphs with microdot apodizers achieve the theoretical performance needed to image Earth-like planets with a range of possible telescope designs, including those with obscured and segmented pupils. A test microdot apodizer with various bulk patterns (step functions, gradients, and sinusoids) and 4 different dot sizes (3, 5, 7, and 10 $\mu$m) made of small chrome squares on anti-reflective glass was characterized with microscopy, optical laser interferometry, as well as transmission and reflectance measurements at wavelengths of 600 and 800 nm. Microscopy revealed the microdots were fabricated to high precision. Results from laser interferometry showed that the phase shifts observed in reflection vary with the local microdot fill factor. Transmission measurements showed that microdot fill factor and transmission were linearly related for dot sizes >5 $\mu$m. However, anomalously high transmittance was measured when the dot size is <5x the wavelength and the fill factor is approximately 50%, where the microdot pattern becomes periodic. The transmission excess is not as prominent in the case of larger dot sizes suggesting that it is likely to be caused by the interaction between the incident field and electronic resonances in the surface of the metallic microdots. We used our empirical models of the microdot apodizers to optimize a second generation of reflective apodizer designs and confirmed that the amplitude and phase of the reflected beam closely matches the ideal wavefront.

[34] arXiv:1807.07211v1 [pdf, vox]

Subband Image Reconstruction using Differential Chromatic Refraction

Matthias Lee, Tamas Budavari, Ian Sullivan, Andrew Connolly
Submitted Thursday 19 July 2018 @ 01:34:58 GMT

Refraction by the atmosphere causes the positions of sources to depend on the airmass through which an observation was taken. This shift is dependent on the underlying spectral energy of the source and the filter or bandpass through which it is observed. Wavelength-dependent refraction within a single passband is often referred to as differential chromatic refraction (DCR). With a new generation of astronomical surveys undertaking repeated observations of the same part of the sky over a range of different airmasses and parallactic angles, DCR should be a detectable and measurable astrometric signal. In this paper we introduce a novel procedure that takes this astrometric signal and uses it to infer the underlying spectral energy distribution of a source; we solve for multiple latent images at specific wavelengths via a generalized deconvolution procedure built on robust statistics. We demonstrate the utility of such an approach for estimating a partially deconvolved image, at higher spectral resolution than the input images, for surveys such as the Large Synoptic Survey Telescope (LSST).

[35] arXiv:1807.07202v1 [pdf, vox]

Gauge-ready formulation of cosmological perturbations in scalar-vector-tensor theories

Lavinia Heisenberg, Ryotaro Kase, Shinji Tsujikawa
Submitted Thursday 19 July 2018 @ 00:47:37 GMT
27 pages

In scalar-vector-tensor (SVT) theories with parity invariance, we perform a gauge-ready formulation of cosmological perturbations on the flat Friedmann-Lema\^{i}t​re-Robertson-Walker (FLRW) background by taking into account a matter perfect fluid. We derive the second-order action of scalar perturbations and resulting linear perturbation equations of motion without fixing any gauge conditions. Depending on physical problems at hand, most convenient gauges can be chosen to study the development of inhomogeneities in the presence of scalar and vector fields coupled to gravity. This versatile framework, which encompasses Horndeski and generalized Proca theories as special cases, is applicable to a wide variety of cosmological phenomena including nonsingular cosmology, inflation, and dark energy. By deriving conditions for the absence of ghost and Laplacian instabilities in several different gauges, we show that, unlike Horndeski theories, it is possible to evade no-go arguments for the absence of stable nonsingular bouncing/genesis solutions in both generalized Proca and SVT theories. We also apply our framework to the case in which scalar and vector fields are responsible for dark energy and find that the separation of observables relevant to the evolution of matter perturbations into tensor, vector, and scalar sectors is transparent in the unitary gauge. Unlike the flat gauge chosen in the literature, this result is convenient to confront SVT theories with observations associated with the cosmic growth history.

[36] arXiv:1807.07195v1 [pdf, vox]

A catalog of merging dwarf galaxies in the local universe

Sanjaya Paudel, Rory Smith, Suk Jin Yoo, Paula Calderón-Castillo, Pierre-Alain Duc
Submitted Thursday 19 July 2018 @ 00:32:47 GMT
26 Pages, Accepted for publication in ApJS

We present the largest publicly available catalog of interacting dwarf galaxies. It includes 177 nearby merging dwarf galaxies of stellar mass M$_{*}$ $<$ 10$^{10}$M$_{\sun}$ and redshifts z $<$ 0.02. These galaxies are selected by visual inspection of publicly available archival imaging from two wide-field optical surveys (SDSS III and the Legacy Survey), and they possess low surface brightness features that are likely the result of an interaction between dwarf galaxies. We list UV and optical photometric data which we use to estimate stellar masses and star formation rates. So far, the study of interacting dwarf galaxies has largely been done on an individual basis, and lacks a sufficiently large catalog to give statistics on the properties of interacting dwarf galaxies, and their role in the evolution of low mass galaxies. We expect that this public catalog can be used as a reference sample to investigate the effects of the tidal interaction on the evolution of star-formation, morphology/structure of dwarf galaxies. Our sample is overwhelmingly dominated by star-forming galaxies, and they are generally found significantly below the red-sequence in the color-magnitude relation. The number of early-type galaxies is only 3 out of 177. We classify them, according to observed low surface brightness features, into various categories including shells, stellar streams, loops, antennae or simply interacting. We find that dwarf-dwarf interactions tend to prefer the low density environment. Only 41 out of the 177 candidate dwarf-dwarf interaction systems have giant neighbors within a sky projected distance of 700 kpc and a line of sight radial velocity range $\pm$700 km/s and, compared to the LMC-SMC, they are generally located at much larger sky-projected distances from their nearest giant neighbor.

[37] arXiv:1807.06664v2 [pdf, vox]

SOFIA/HAWC+ detection of a gravitationally lensed starburst galaxy at $z$ = 1.03

Jingzhe Ma, Arianna Brown, Asantha Cooray, Hooshang Nayyeri, Hugo Messias, Nicholas Timmons, Johannes Staguhn, Pasquale Temi, C. Darren Dowell, Julie Wardlow, Dario Fadda, Attila Kovacs, Dominik Riechers, Ivan Oteo, Derek Wilson, Ismael Perez-Fournon
Submitted Thursday 19 July 2018 @ 00:31:38 GMT
8 pages, 3 figures; accepted for publication in ApJ

We present the detection at 89 $\mu$m (observed frame) of the {\it Herschel}-selected gravitationally lensed starburst galaxy HATLASJ1429-0028 (also known as G15v2.19) in 15 minutes with the High-resolution Airborne Wideband Camera-plus (HAWC+) onboard the Stratospheric Observatory for Infrared Astronomy (SOFIA). The spectacular lensing system consists of an edge-on foreground disk galaxy at $z$ = 0.22 and a nearly complete Einstein ring of an intrinsic ultra-luminous infrared galaxy at $z$ = 1.03. Is this high IR luminosity powered by pure star formation (SF) or also an active galactic nucleus (AGN)? Previous nebular line diagnostics indicate that it is star-formation dominated. We perform a 27-band multi-wavelength spectral energy distribution modeling (SED) including the new SOFIA/HAWC+ data to constrain the fractional AGN contribution to the total IR luminosity. The AGN fraction in the IR turns out to be negligible. In addition, J1429-0028 serves as a testbed for comparing SED results from different models/templates and SED codes (MAGPHYS, SED3FIT, and CIGALE). We stress that star formation history is the dominant source of uncertainty in the derived stellar mass (as high as a factor of $\sim$ 10) even in the case of extensive photometric coverage. Furthermore, the detection of a source at $z$ $\sim$ 1 with SOFIA/HAWC+ demonstrates the potential of utilizing this facility for distant galaxy studies including the decomposition of SF/AGN components, which cannot be accomplished with other current facilities.

Submitted Wed, 18 Jul 2018

[38] arXiv:1807.07182v1 [pdf, vox]

Simulating an Isolated Dwarf Galaxy with Multi-Channel Feedback and Chemical Yields from Individual Stars

Andrew Emerick, Greg L. Bryan, Mordecai-Mark Mac Low
Submitted Wednesday 18 July 2018 @ 23:23:42 GMT
21 pages, 13 figures (plus 5 page, 6 figure appendix). Re-submitted to MNRAS after first revisions

In order to better understand the relationship between feedback and galactic chemical evolution, we have developed a new model for stellar feedback at grid resolutions of only a few parsecs in global disk simulations, using the adaptive mesh refinement hydrodynamics code Enzo. For the first time in galaxy scale simulations, we simulate detailed stellar feedback from individual stars including asymptotic giant branch winds, photoelectric heating, Lyman-Werner radiation, ionizing radiation tracked through an adaptive ray-tracing radiative transfer method, and core collapse and Type Ia supernovae. We furthermore follow the star-by-star chemical yields using tracer fields for 15 metal species: C, N, O, Na, Mg, Si, S, Ca, Mn, Fe, Ni, As, Sr, Y, and Ba. We include the yields ejected in massive stellar winds, but greatly reduce the winds' velocities due to computational constraints. We describe these methods in detail in this work and present the first results from 500 Myr of evolution of an isolated dwarf galaxy with properties similar to a Local Group, low-mass dwarf galaxy. We demonstrate that our physics and feedback model is capable of producing a dwarf galaxy whose evolution is consistent with observations in both the Kennicutt-Schmidt relationship and extended Schmidt relationship. Effective feedback drives outflows with a greater metallicity than the ISM, leading to low metal retention fractions consistent with observations. Finally, we demonstrate that these simulations yield valuable information on the variation in mixing behavior of individual metal species within the multi-phase interstellar medium.

[39] arXiv:1807.07179v1 [pdf, vox]

Characterization of lemniscate atmospheric aberrations in Gemini Planet Imager data

Alexander Madurowicz, Bruce A. Macintosh, Jean-Baptiste Ruffio, Jeffery Chilcote, Vanessa P. Bailey, Lisa Poyneer, Eric Nielsen, Andrew P. Norton
Submitted Wednesday 18 July 2018 @ 22:45:35 GMT
13 pages, 8 figures, Proceedings of SPIE 10703-230

A semi analytic framework for simulating the effects of atmospheric seeing in Adaptive Optics systems on an 8-m telescope is developed with the intention of understanding the origin of the wind-butterfly, a characteristic two-lobed halo in the PSF of AO imaging. Simulations show that errors in the compensated phase on the aperture due to servo-lag have preferential direction orthogonal to the direction of wind propagation which, when Fourier Transformed into the image plane, appear with their characteristic lemniscate shape along the wind direction. We develop a metric to quantify the effect of this aberration with the fractional standard deviation in an annulus centered around the PSF, and use telescope pointing to correlate this effect with data from an atmospheric models, the NOAA GFS. Our results show that the jet stream at altitudes of 100-200 hPa (equivalently 10-15 km above sea level) is highly correlated (13.2$\sigma$) with the strong butterfly, while the ground wind and other layers are more or less uncorrelated.

[40] arXiv:1807.07178v1 [pdf, vox]

V1369 Cen high resolution panchromatic late nebular spectra in the context of a unified picture for nova ejecta

Elena Mason, Steven N. Shore, Ivan De Gennaro Aquino, Luca Izzo, Kim Page, Greg J. Schwarz
Submitted Wednesday 18 July 2018 @ 22:45:32 GMT

Nova Cen 2013 (V1369 Cen) is the fourth bright nova observed panchromatically through high resolution UV+optical multi epoch spectroscopy. It is also the nova with the richest set of spectra (both in terms of data quality and number of epochs) thanks to its exceptional brightness. Here, we use the late nebular spectra taken between day ~250 and day ~837 after outburst to derive the physical, geometrical and kinematical properties of the nova. We compare the results with those determined for the other panchromatic studies in this series: T Pyx, V339 Del (nova Del 2013), and V959 Mon (nova Mon 2012). From this we conclude that in all these novae the ejecta geometry and phenomenology can be consistently explained by clumpy gas expelled during a single, brief ejection episode and in ballistic expansion, and not by a wind. For V1369 Cen the ejecta mass (about 1E-4 solar masses) and filling factor (0.1<=f<=0.2) are consistent with those of classical novae but larger (by at least an order of magnitude) than those of T Pyx and the recurrent novae. V1369 Cen has an anomalously high relative to solar N/C ratio that is beyond the range currently predicted for a CO nova, and the Ne emission line strengths are dissimilar to those of typical ONe or CO white dwarfs.

[41] arXiv:1807.07176v1 [pdf, vox]

Axion Cosmology with Early Matter Domination

Ann E. Nelson, Huangyu Xiao
Submitted Wednesday 18 July 2018 @ 22:44:25 GMT
9 pages, 3 figures

The default assumption of early universe cosmology is that the postinflationary universe was radiation dominated until it was about 47000 years old. Direct evidence for the radiation dominated epoch extends back until nucleosynthesis, which began during the first second. However there are theoretical reasons to prefer a period of earlier matter domination, prior to nucleosynthesis, e.g. due to late decaying massive particles needed to explain baryogenesis. Axion cosmology is quantitatively affected by an early period of matter domination, with a different axion mass range preferred and greater inhomogeneity produced on small scales. In this work we show that such increased inhomogeneity can lead to the formation of axion miniclusters in axion parameter ranges that are different from those usually assumed. If the reheating temperature is below $58$ MeV, axion miniclusters can form even if the axion field is present during inflation and has been previously homogenized. The upper bound on the typical initial axion minicluster mass is raised from $10^{-10} M_{\odot}$ to $10^{-7} M_{\odot}$, where $M_{\odot}$ is a solar mass. These results may have consequences for indirect detection of axion miniclusters, and could conceivably probe the thermal history of the universe before nucleosynthesis.

[42] arXiv:1807.04037v2 [pdf, vox]

PyUltraLight: A Pseudo-Spectral Solver for Ultralight Dark Matter Dynamics

Faber Edwards, Emily Kendall, Shaun Hotchkiss, Richard Easther
Submitted Wednesday 18 July 2018 @ 22:26:36 GMT
available at: https://github.com/a​uckland-cosmo/PyUltr​aLight

PyUltraLight simulates the dynamics of ultralight dark matter in a non-expanding background. PyUltraLight can describe the evolution of several interacting ultralight dark matter halos or one or more halos orbiting a central, fixed Newtonian potential, the latter scenario corresponding to dwarf galaxies orbiting a massive central galaxy. We verify PyUltraLight by showing that it reproduces qualitative dynamical features of previously published simulations and demonstrate that it has excellent energy-conservation properties. PyUltraLight is implemented in a Python-based Jupyter notebook, solving the Schrodinger-Poisson equation governing ultralight scalar field dark matter dynamics in the non-relativistic regime using a symmetrised split-step pseudospectral algorithm. The notebook interface makes it simple to specify simulation parameters and visualise the resulting output but performance-critical routines are managed via calls to computationally efficient compiled libraries. PyUltraLight runs on standard desktop hardware with support for shared memory mutlithreading and is available on GitHub.

[43] arXiv:1807.07174v1 [pdf, vox]

Spectroscopic diagnostics of dust formation and evolution in classical nova ejecta

Steven N. Shore, N. Paul Kuin, Elena Mason, Ivan De Gennaro Aquino
Submitted Wednesday 18 July 2018 @ 22:22:35 GMT
15 pages 14 figures, accepted for publication in A&A, 2018 June 28

A fraction of classical novae form dust during the early stages of their outbursts. The classical CO nova V5668 Sgr (Nova Sgr. 2015b) underwent a deep photometric minimum about 100 days after outburst that was covered across the spectrum. A similar event was observed for an earlier CO nova, V705 Cas (Nova Cas 1993) and a less optically significant event for the more recent CO nova V339 Del (Nova Del 2013). This study provides a "compare and contrast" of these events to better understand the very dynamical event of dust formation. We show the effect of dust formation on multiwavelength high resolution line profiles in the interval 1200\AA\ - 9200\AA\ using a biconical ballistic structure that has been applied in our previous studies of the ejecta. We find that both V5668 Sgr and V339 Del can be modeled using a grey opacity for the dust, indicating fairly large grains (at least 0.1 micron) and that the persistent asymmetries of the line profiles in late time spectra, up to 650 days after the event for V5668 Sgr and 866 days for V339 Del, point to the survival of the dust well into the transparent, nebular stage of the ejecta evolution. This is a general method for assessing the properties of dust forming novae well after the infrared is completely transparent in the ejecta.

[44] arXiv:1807.07169v1 [pdf, vox]

CNO Solar Neutrinos in Next-Generation Dark Matter Experiments

Jayden L. Newstead, Louis E. Strigari, Rafael F. Lang
Submitted Wednesday 18 July 2018 @ 22:03:25 GMT
8 pages, 5 figures

We study the prospects for measuring the low-energy components of the solar neutrino flux in future direct dark matter detection experiments. We show that for a depletion of $^{136}$Xe by a factor of 100 relative to its natural abundance, and an extension to electron recoil energies of $\sim$ MeV, future xenon experiments with exposure $\sim 200$ ton-yr can detect the CNO component of the solar neutrino flux at $\sim 3 \sigma$ significance. A CNO detection will provide important insight into metallicity of the solar interior. Precise measurement of low-energy solar neutrinos, including as $pp$, $^7$Be, and $pep$ components, will further improve constraints on the "neutrino luminosity" of the Sun, thereby providing constraints on alternative sources of energy production. We find that a measurement of $L_{\nu}/L_{\odot}$ of order one percent is possible with the above exposure, improving on current bounds from a global analysis of solar neutrino data by a factor of about seven.

[45] arXiv:1807.07164v1 [pdf, vox]

A novel single-pulse search approach to detection of dispersed radio pulses using clustering and supervised machine learning

Di Pang, Katerina Goseva-Popstojanova, Thomas Devine, Maura McLaughlin
Submitted Wednesday 18 July 2018 @ 21:32:34 GMT
22 pages, accepted for publication in MNRAS, ref. MN-17-3830-MJ.R2

We present a novel two-stage approach which combines unsupervised and supervised machine learning to automatically identify and classify single pulses in radio pulsar search data. In the first stage, we identify astrophysical pulse candidates in the data, which were derived from the Pulsar Arecibo L-Band Feed Array (PALFA) survey and contain 47,042 independent beams, as trial single-pulse event groups (SPEGs) by clustering single-pulse events and merging clusters that fall within the expected DM and time span of astrophysical pulses. We also present a new peak scoring algorithm, to identify astrophysical peaks in S/N versus DM curves. Furthermore, we group SPEGs detected at a consistent DM for they were likely emitted by the same source. In the second stage, we create a fully labelled benchmark data set by selecting a subset of data with SPEGs identified (using stage 1 procedures), their features extracted and individual SPEGs manually labelled, and then train classifiers using supervised machine learning. Next, using the best trained classifier, we automatically classify unlabelled SPEGs identified in the full data set. To aid the examination of dim SPEGs, we develop an algorithm that searches for an underlying periodicity among grouped SPEGs. The results showed that RandomForest with SMOTE treatment was the best learner, with a recall of 95.6% and a false positive rate of 2.0%. In total, besides all 60 known pulsars from the benchmark data set, the model found 32 additional (i.e., not included in the benchmark data set) known pulsars, and several potential discoveries.

[46] arXiv:1807.07160v1 [pdf, vox]

Possible GeV counterpart at the ground level associated with Fermi LAT gamma-ray bursts

C. R. A. Augusto, C. E. Navia, M. N. de Oliveira, A. Nepomuceno, V. Kopenkin, T. Sinzi
Submitted Wednesday 18 July 2018 @ 21:20:25 GMT
25 pages, 14 figures. Accepted in J. Phys. Commun

From June 2014 to February 2017, the Fermi LAT detected 46 gamma-ray bursts (GRBs) with photon energies above 20 MeV, and the trigger coordinates of seven of them were within the FoV of New-Tupi detector located in the central region of the South Atlantic Anomaly (SAA). We show in this paper that two of these seven GRBs have a probable GeV counterpart observed at ground level by New-Tupi detector. The first is GRB 160609A, a short duration GRB with a bright emission of photons over a broad energy range extending up to GeV energies. The second is GRB 160625B, a very long duration GRB, for which the Fermi LAT detected more than 300 photons with energies above 100 MeV in the $\sim$ 1 ks interval after the GBM trigger. In the first case, the signal at New-Tupi has a nominal significance of $3.5\sigma$ in the counting rate time profiles, within the T90($=5.6$ s) duration on Fermi GBM. However, the effective significance is only $3.0\sigma$. In the second case, New-Tupi detector registered at least two excess (peaks) with a nominal statistical significance of $4.8\sigma$ and $5.0\sigma$ at 438 s and 558 s after the trigger. The first is within the $T90(=460$ s) on Fermi GBM. Even so, the effective significance is only $\sim 2.0\sigma$. In addition, from a Monte Carlo analysis, we show that the expected signal-to-noise ratio is compatible with the observation of GRB 160709A, only if the differential index of the GRB energy spectrum be equal or higher than -2.2 (a non-steep spectrum).

[47] arXiv:1807.07157v1 [pdf, vox]

Air, Telescope, and Instrument Temperature Effects on the Gemini Planet Imager's Image Quality

Melisa Tallis, Vanessa P. Bailey, Bruce Macintosh, Jeffrey K. Chilcote, Lisa A. Poyneer, Jean-Baptiste Ruffio, Thomas L. Hayward, Dmitry Savransky
Submitted Wednesday 18 July 2018 @ 21:12:45 GMT
6 pages, 6 figures, 2018 SPIE Proceedings (10703-267)

The Gemini Planet Imager (GPI) is a near-infrared instrument that uses Adaptive Optics (AO), a coronagraph, and advanced data processing techniques to achieve very high contrast images of exoplanets. The GPI Exoplanet Survey (GPIES) is a 600 stars campaign aiming at detecting and characterizing young, massive and self-luminous exoplanets at large orbital distances >5 au. Science observations are taken simultaneously with environmental data revealing information about the turbulence in the telescope environment as well as limitations of GPI's AO system. Previous work has shown that the timescale of the turbulence, Tau0, is a strong predictor of AO performance, however an analysis of the dome turbulence on AO performance has not been done before. Here, we study correlations between image contrast and residual wavefront error (WFE) with temperature measurements from multiple locations inside and outside the dome. Our analysis revealed GPI's performance is most correlated with the temperature difference between the primary mirror of the telescope and the outside air. We also assess the impact of the current temperature control and ventilation strategy at Gemini South (GS).

[48] arXiv:1807.07153v1 [pdf, vox]

Mining the GPIES database

Dmitry Savransky, Jacob Shapiro, Vanessa Bailey, Robert De Rosa, Jason Wang, Jean-Baptiste Ruffio, Eric Nielsen, Melisa Tallis, Marshall Perrin
Submitted Wednesday 18 July 2018 @ 21:09:38 GMT
15 pages, 11 Figures. Presented at SPIE Astronomical Telescopes + Instrumentation, 2018, Austin, Texas, United States. Adaptive Optics Systems VI, 107030H (10 July 2018)

The Gemini Planet Imager Exoplanet Survey (GPIES) is a direct imaging campaign designed to search for young, self-luminous, giant exoplanets. To date, GPIES has observed nearly 500 targets, and generated over 30,000 individual exposures using its integral field spectrograph (IFS) instrument. The GPIES team has developed a campaign data system with a database incorporating all of the metadata for all individual raw data products, including environmental conditions and instrument performance metrics. The same database also indexes metadata associated with multiple levels of reduced data products, including contrast measures for individual images and combined image sequences, which serve as the primary metric of performance for the final science products. The database is also used to track telemetry products from the adaptive optics subsystem, and associate these with corresponding IFS data. Here, we discuss several data exploration and visualization projects enabled by the GPIES database. Of particular interest are any correlations between instrument performance and environmental or operating conditions. We show single and multiple-parameter fits of single-image and observing sequence contrast as functions of various seeing measures, and discuss automated outlier rejection and other fitting concerns. Supervised learning techniques are employed in order to partition the space of raw (single image) to final (full sequence) contrast in order to better predict the value of the final data set from the first few completed observations. Finally, we discuss the particular features of the database design that aid in performing these analyses, and suggest potential future upgrades and refinements.

[49] arXiv:1807.07146v1 [pdf, vox]

The Gemini Planet Imager: Looking back over five years and forward to the future

Bruce Macintosh, Jeffrey K. Chilcote, Vanessa P. Bailey, Robert De Rosa, Eric Nielsen, Andrew Norton, Lisa Poyneer, Jason Wang, J. B. Ruffio, J. R. Graham, Christian Marois, Dmitry Savransky, Jean-Pierre Veran
Submitted Wednesday 18 July 2018 @ 21:05:10 GMT
To appear in Proceedings of the SPIE 10703 (Adaptive Optics Systems VI)

The Gemini Planet Imager (GPI), a coronagraphic adaptive optics instrument designed for spectroscopy of extrasolar planets, had first light in 2013[13]. After five years, GPI has observed more than 500 stars, producing an extensive library of science images and associated telemetry that can be analyzed to determine performance predictors. We will present a summary of on-sky performance and lessons learned. The two most significant factors determining bright star contrast performance are atmospheric coherence time and the presence of dome seeing. With a possible move to Gemini North, we are planning potential upgrades including a pyramid-sensor based AO system with predictive control; we will summarize upgrade options and the science they would enable.

[50] arXiv:1807.07145v1 [pdf, vox]

Upgrading the Gemini Planet Imager: GPI 2.0

Jeffrey K. Chilcote, Vanessa P. Bailey, Rob De Rosa, Bruce Macintosh, Eric Nielsen, Andrew Norton, Maxwell A. Millar-Blanchaer, James Graham, Christian Marois, Laurent Pueyo, Julien Rameau, Dmitry Savransky, Jean-Pierre Veran
Submitted Wednesday 18 July 2018 @ 21:05:01 GMT
14 pages, 6 figures, 1 table

The Gemini Planet Imager (GPI) is the dedicated high-contrast imaging facility, located on Gemini South, designed for the direct detection and characterization of young Jupiter mass exoplanets. In 2019, Gemini is considering moving GPI from Gemini South to Gemini North. Analysis of GPI's as-built performance has highlighted several key areas of improvement to its detection capabilities while leveraging its current capabilities as a facility class instrument. We present the proposed upgrades which include a pyramid wavefront sensor, broadband low spectral resolution prisms and new apodized-pupil Lyot coronagraph designs all of which will enhance the current science capabilities while enabling new science programs.

[51] arXiv:1807.07140v1 [pdf, vox]

Experimental validation of joint phase and amplitude wave-front sensing with coronagraphic phase diversity for high-contrast imaging

Olivier Herscovici-Schiller, Laurent M. Mugnier, Pierre Baudoz, Raphaël Galicher, Jean-François Sauvage, Baptiste Paul
Submitted Wednesday 18 July 2018 @ 20:46:43 GMT
Reproduced with permission from Astronomy & Astrophysics, Copyright ESO

Context. The next generation of space-borne instruments dedicated to the direct detection of exoplanets requires unprecedented levels of wavefront control precision. Coronagraphic wavefront sensing techniques for these instruments must measure both the phase and amplitude of the optical aberrations using the scientific camera as a wavefront sensor. Aims. In this paper, we develop an extension of coronagraphic phase diversity to the estimation of the complex electric field, that is, the joint estimation of phase and amplitude. Methods. We introduced the formalism for complex coronagraphic phase diversity. We have demonstrated experimentally on the Tr\`es Haute Dynamique testbed at the Observatoire de Paris that it is possible to reconstruct phase and amplitude aberrations with a subnanometric precision using coronagraphic phase diversity. Finally, we have performed the first comparison between the complex wavefront estimated using coronagraphic phase diversity (which relies on time-modulation of the speckle pattern) and the one reconstructed by the self-coherent camera (which relies on the spatial modulation of the speckle pattern). Results. We demonstrate that coronagraphic phase diversity retrieves complex wavefront with subnanometric precision with a good agreement with the reconstruction performed using the self-coherent camera. Conclusions. This result paves the way to coronagraphic phase diversity as a coronagraphic wave-front sensor candidate for very high contrast space missions.

[52] arXiv:1807.07113v1 [pdf, vox]

A search for annual and diurnal rate modulations in the LUX experiment

D. S. Akerib, S. Alsum, H. M. Araújo, X. Bai, A. J. Bailey, J. Balajthy, P. Beltrame, E. P. Bernard, A. Bernstein, T. P. Biesiadzinski, E. M. Boulton, P. Brás, D. Byram, M. C. Carmona-Benitez, C. Chan, A. Currie, J. E. Cutter, T. J. R. Davison, A. Dobi, E. Druszkiewicz, S. R. Fallon, A. Fan, S. Fiorucci, R. J. Gaitskell, J. Genovesi, C. Ghag, M. G. D. Gilchriese, C. R. Hall, S. J. Haselschwardt, S. A. Hertel, D. P. Hogan, M. Horn, D. Q. Huang, C. M. Ignarra, R. G. Jacobsen, W. Ji, K. Kamdin, K. Kazkaz, D. Khaitan, R. Knoche, E. V. Korolkova, V. A. Kudryavtsev, B. G. Lenardo, K. T. Lesko, J. Liao, A. Lindote, M. I. Lopes, A. Manalaysay, R. L. Mannino, N. Marangou, M. F. Marzioni, D. N. McKinsey, D. -M. Mei, J. Mock, M. Moongweluwan, J. A. Morad, A. St. J. Murphy, C. Nehrkorn, H. N. Nelson, F. Neves, K. O'Sullivan, K. C. Oliver-Mallory, K. J. Palladino, E. K. Pease, C. Rhyne, P. Rossiter, S. Shaw, T. A. Shutt, C. Silva, M. Solmaz, V. N. Solovov, P. Sorensen, T. J. Sumner, M. Szydagis, D. J. Taylor, W. C. Taylor, B. P. Tennyson, P. A. Terman, D. R. Tiedt, W. H. To, M. Tripathi, L. Tvrznikova, U. Utku, S. Uvarov, V. Velan, J. R. Verbus, R. C. Webb, J. T. White, T. J. Whitis, M. S. Witherell, F. L. H. Wolfs, D. Woodward, J. Xu, K. Yazdani, S. K. Young, C. Zhang
Submitted Wednesday 18 July 2018 @ 19:27:07 GMT
12 pages, 9 figures

Various dark matter models predict annual and diurnal modulations of dark matter interaction rates in Earth-based experiments as a result of the Earth's motion in the halo. Observation of such features can provide generic evidence for detection of dark matter interactions. In this paper, we report a search for both annual and diurnal rate modulations in the LUX dark matter experiment using over 20 calendar months of data acquired between 2013 and 2016. This search focuses on electron recoil events at low energies, where leptophilic dark matter interactions are expected to occur and where the DAMA experiment has observed a strong rate modulation for over two decades. By using the innermost volume of the LUX detector and developing robust cuts and corrections, we obtained a stable event rate of 2.3$\pm$0.2 cpd/keV$_{\text{ee}}​$/tonne, which is among the lowest in all dark matter experiments. No statistically significant annual modulation was observed in energy windows up to 26 keV$_{\text{ee}}$. Between 2 and 6 keV$_{\text{ee}}$, this analysis demonstrates the most sensitive annual modulation search up to date, with 9.2 $\sigma$ tension with the DAMA/LIBRA result. We also report no observation of diurnal modulations above 0.2 cpd/keV$_{\text{ee}}​$/tonne amplitude between 2 and 6 keV$_{\text{ee}}$.

[53] arXiv:1807.07100v1 [pdf, vox]

Review of high-contrast imaging systems for current and future ground-based and space-based telescopes III. Technology opportunities and pathways

Frans Snik, Olivier Absil, Pierre Baudoz, Mathilde Beaulieu, Eduardo Bendek, Eric Cady, Brunella Carlomagno, Alexis Carlotti, Nick Cvetojevic, David Doelman, Kevin Fogarty, Raphaël Galicher, Olivier Guyon, Sebastiaan Haffert, Elsa Huby, Jeffrey Jewell, Nemanja Jovanovic, Christoph Keller, Matthew Kenworthy, Justin Knight, Jonas Kühnn, Johan Mazoyer, Kelsey Miller, Mamadou N'Diaye, Barnaby Norris, Emiel Por, Laurent Pueyo, A J Eldorado Riggs, Garreth Ruane, Dan Sirbu, J. Kent Wallace, Michael Wilby, Marie Ygouf
Submitted Wednesday 18 July 2018 @ 18:42:47 GMT

The Optimal Optical CoronagraphWorkshop at the Lorentz Center in September 2017 in Leiden, the Netherlands gathered a diverse group of 25 researchers working on exoplanet instrumentation to stimulate the emergence and sharing of new ideas. This contribution is the final part of a series of three papers summarizing the outcomes of the workshop, and presents an overview of novel optical technologies and systems that are implemented or considered for high-contrast imaging instruments on both ground-based and space telescopes. The overall objective of high contrast instruments is to provide direct observations and characterizations of exoplanets at contrast levels as extreme as 10^-10. We list shortcomings of current technologies, and identify opportunities and development paths for new technologies that enable quantum leaps in performance. Specifically, we discuss the design and manufacturing of key components like advanced deformable mirrors and coronagraphic optics, and their amalgamation in "adaptive coronagraph" systems. Moreover, we discuss highly integrated system designs that combine contrast-enhancing techniques and characterization techniques (like high-resolution spectroscopy) while minimizing the overall complexity. Finally, we explore extreme implementations using all-photonics solutions for ground-based telescopes and dedicated huge apertures for space telescopes.

[54] arXiv:1807.07098v1 [pdf, vox]

The first super-Earth Detection from the High Cadence and High Radial Velocity Precision Dharma Planet Survey

Bo Ma, Jian Ge, Matthew Muterspaugh, Michael A. Singer, Gregory W. Henry, Jonay I. Gonzalez Hernandez, Sirinrat Sithajan, Sarik Jeram, Michael Williamson, Keivan Stassun, Benjamin Kimock, Frank Varosi, Sidney Schofield, Jian Liu, Scott Powell, Anthony Cassette, Hali Jakeman, Louis Avner, Nolan Grieves, Rory Barnes, Sankalp Gilda, Jim Grantham, Greg Stafford, David Savage, Steve Bland, Brent Ealey
Submitted Wednesday 18 July 2018 @ 18:39:59 GMT
13 pages, 17 figures, Accepted for publication in MNRAS

The Dharma Planet Survey (DPS) aims to monitor about 150 nearby very bright FGKM dwarfs (within 50 pc) during 2016$-$2020 for low-mass planet detection and characterization using the TOU very high resolution optical spectrograph (R$\approx$100,000, 380-900nm). TOU was initially mounted to the 2-m Automatic Spectroscopic Telescope at Fairborn Observatory in 2013-2015 to conduct a pilot survey, then moved to the dedicated 50-inch automatic telescope on Mt. Lemmon in 2016 to launch the survey. Here we report the first planet detection from DPS, a super-Earth candidate orbiting a bright K dwarf star, HD 26965. It is the second brightest star ($V=4.4$ mag) on the sky with a super-Earth candidate. The planet candidate has a mass of 8.47$\pm0.47M_{\rm Earth}$, period of $42.38\pm0.01$ d, and eccentricity of $0.04^{+0.05}_{-0.03​}$. This RV signal was independently detected by Diaz et al. (2018), but they could not confirm if the signal is from a planet or from stellar activity. The orbital period of the planet is close to the rotation period of the star (39$-$44.5 d) measured from stellar activity indicators. Our high precision photometric campaign and line bisector analysis of this star do not find any significant variations at the orbital period. Stellar RV jitters modeled from star spots and convection inhibition are also not strong enough to explain the RV signal detected. After further comparing RV data from the star's active magnetic phase and quiet magnetic phase, we conclude that the RV signal is due to planetary-reflex motion and not stellar activity.

[55] arXiv:1807.07094v1 [pdf, vox]

ARC: Adaptive Ray-tracing with CUDA, a New Ray Tracing Code for Parallel GPUs

Blake Hartley, Massimo Ricotti
Submitted Wednesday 18 July 2018 @ 18:20:22 GMT
18 pages, 13 figures

We present the methodology of a photon-conserving, spatially-adaptive, ray-tracing radiative transfer algorithm, designed to run on multiple parallel Graphic Processing Units (GPUs). Each GPU has thousands computing cores, making them ideally suited to the task of tracing independent rays. This ray-tracing implementation has speed competitive with approximate momentum methods, even with thousands of ionization sources, without sacrificing accuracy and resolution. Here, we validate our implementation with the selection of tests presented in the "cosmological radiative transfer codes comparison project," to demonstrate the correct behavior of the code. We also present a selection of benchmarks to demonstrate the performance and computational scaling of the code. As expected, our method scales linearly with the number of sources and with the square of the dimension of the 3D computational grid. Our current implementation is scalable to an arbitrary number of nodes possessing GPUs, but is limited to a uniform resolution 3D grid. Cosmological simulations of reionization with tens of thousands of radiation sources and intergalactic volumes sampled with 1024$^3$ grid points take about 30 days on 64 GPUs to reach complete reionization.

[56] arXiv:1807.07093v1 [pdf, vox]

Abundance matching with the mean star formation rate: there is no missing satellites problem in the Milky Way

J. I. Read, D. Erkal
Submitted Wednesday 18 July 2018 @ 18:17:59 GMT
13 pages, 7 figures. Submitted to MNRAS. Comments welcome!

Classical abundance matching has been shown to produce mass estimates, $M^{\rm abund}_{200}$, that agree well with independent dynamical estimates, $M^{\rm dyn}_{200}$, for isolated dwarfs. However, for satellite galaxies, it is expected to fail. This is because tidal stripping lowers $M_*$ and $M^{\rm dyn}_{200}$, causing satellites to scatter above the $M_*-M_{200}$ relation for isolated dwarfs, while ram-pressure stripping quenches star formation on infall, causing satellites to scatter below the relation. In this paper, we introduce a novel abundance matching technique that produces a more accurate estimate of $M_{200}$ for satellite galaxies. To achieve this, we abundance match with the mean star formation rate, averaged over the time when a galaxy was forming stars, $\langle {\rm SFR}\rangle$, instead of $M_*$. Using data from the Sloan Digital Sky Survey and the Bolshoi simulation, we obtain a statistical $\langle {\rm SFR}\rangle-{\rm M}_{200}$ relation in $\Lambda{\rm CDM}$. We then compare $M^{\rm abund}_{200}$ derived from this relation with $M^{\rm dyn}_{200}$ for 21 nearby dSph and dIrr galaxies, finding a good agreement between the two. As a first application, we use our new $\langle {\rm SFR}\rangle-{\rm M}_{200}$ relation to empirically measure the cumulative mass function of a volume-complete sample of bright Milky Way satellites within 280 kpc of the Galactic centre. We compare this with a suite of cosmological 'zoom' simulations of Milky Way-mass halos that account for subhalo depletion by the Milky Way disc. Including a conservative lower bound on the number of 'ultra-faint' dwarfs in this same volume, we find no missing satellites problem above $M_{200} \sim 10^9$M$_\odot$ in the Milky Way. We discuss how this empirical method can be applied to a larger sample of spiral galaxies in the Local Volume.

[57] arXiv:1807.07089v1 [pdf, vox]

Distances to the globular clusters 47 Tucanae and NGC 362 using Gaia DR2 parallaxes

Seery Chen, Harvey Richer, Ilaria Caiazzo, Jeremy Heyl
Submitted Wednesday 18 July 2018 @ 18:09:40 GMT
15 pages, 8 figures, submitted to ApJ

Using parallaxes from Gaia DR2, we estimate the distance to the globular clusters 47 Tuc and NGC 362, taking advantage of the background stars in the Small Magellanic Cloud and quasars to account for various parallax systematics. We found the parallax to be dependent on the Gaia DR2 g apparent magnitude for stars with $13<\textrm{g}<18$ , where brighter stars have a lower parallax zero point than fainter stars. The distance to 47 Tuc was found to be $4.45\pm0.01\pm0.12$ kpc, and for NGC 362 $8.54\pm0.20\pm0.44$ kpc with random and systematic errors listed respectively. This is the first time a precise distance measurement directly using parallaxes has been done for either of these two globular clusters.

[58] arXiv:1807.07084v1 [pdf, vox]

A Quantification of the Butterfly Effect in Cosmological Simulations and Implications for Galaxy Scaling Relations

Shy Genel, Greg L. Bryan, Volker Springel, Lars Hernquist, Dylan Nelson, Annalisa Pillepich, Rainer Weinberger, Ruediger Pakmor, Federico Marinacci, Mark Vogelsberger
Submitted Wednesday 18 July 2018 @ 18:00:08 GMT
Key figures: 9 & 10

We study the chaotic-like behavior of cosmological simulations by quantifying how minute perturbations grow over time and manifest as macroscopic differences in galaxy properties. When we run the same setup multiple times, the results produced by our code, Arepo, are binary identical. However, when we run pairs of 'shadow' simulations that are identical except for random minute initial displacements to particle positions (e.g. of order 10^-7pc), the results diverge from each other at the individual galaxy level (while the statistical properties of the ensemble of galaxies are unchanged). After cosmological times, the global properties of pairs of 'shadow' galaxies that are matched between the simulations differ from each other generally at a level of ~2-25%, depending on the considered physical quantity. We perform these experiments using cosmological volumes of (25-50Mpc/h)^3 evolved either purely with dark matter, or with baryons and star-formation but no feedback, or using the full feedback model of the IllustrisTNG project. The runs cover four resolution levels spanning a factor of 512 in mass. We find that without feedback the differences between shadow galaxies generally become smaller as the resolution increases, but with the IllustrisTNG model the results are mostly converging towards a 'floor'. This hints at the role of feedback in setting the chaotic properties of galaxy formation. Importantly, we compare the macroscopic differences between shadow galaxies to the overall scatter in various galaxy scaling relations, and conclude that for the star formation-mass and the Tully-Fisher relations the chaotic behavior of our simulations contributes significantly to the overall scatter. We discuss the implications for galaxy formation theory in general and for cosmological simulations in particular.

[59] arXiv:1807.07080v1 [pdf, vox]

Far-infrared Herschel SPIRE spectroscopy of lensed starbursts reveals physical conditions of ionised gas

Zhi-Yu Zhang, R. J. Ivison, R. D. George, Yinghe Zhao, L. Dunne, R. Herrera-Camus, A. J. R. Lewis, Daizhong Liu, D. Naylor, Ivan Oteo, D. A. Riechers, Ian Smail, Chentao Yang, Stephen Eales, Ros Hopwood, Steve Maddox, Alain Omont, Paul van der Werf
Submitted Wednesday 18 July 2018 @ 18:00:03 GMT
39 pages, 19 figures, Accepted for publication in MNRAS. For extra pptx slides prepared for this work, please see http://www.eso.org/~​zzhang/download/FTS_​SMG_survey_ZhiyuZhan​g.pdf

The most intensively star-forming galaxies are extremely luminous at far-infrared (FIR) wavelengths, highly obscured at optical and ultraviolet wavelengths, and lie at $z\ge 1-3$. We present a programme of ${\it Herschel}$ FIR spectroscopic observations with the SPIRE FTS and photometric observations with PACS, both on board ${\it Herschel}$, towards a sample of 45 gravitationally lensed, dusty starbursts across $z\sim 1-3.6$. In total, we detected 27 individual lines down to 3-$\sigma$, including nine $[\rm C{\small II}]$ 158-$\mu$m lines with confirmed spectroscopic redshifts, five possible $[\rm C{\small II}]$ lines consistent with their far-infrared photometric redshifts, and in some individual sources a few $[\rm O{\small III}]$ 88-$\mu$m, $[\rm O{\small III}]$ 52-$\mu$m, $[\rm O{\small I}]$ 145-$\mu$m, $[\rm O{\small I}]$ 63-$\mu$m, $[\rm N{\small II}]$ 122-$\mu$m, and OH 119-$\mu$m (in absorption) lines. To derive the typical physical properties of the gas in the sample, we stack all spectra weighted by their intrinsic luminosity and by their 500-$\mu$m flux densities, with the spectra scaled to a common redshift. In the stacked spectra, we detect emission lines of $[\rm C{\small II}]$ 158-$\mu$m, $[\rm N{\small II}]$ 122-$\mu$m, $[\rm O{\small III}]$ 88-$\mu$m, $[\rm O{\small III}]$ 52-$\mu$m, $[\rm O{\small I}]$ 63-$\mu$m, and the absorption doublet of OH at 119-$\mu$m, at high fidelity. We find that the average electron densities traced by the $[\rm N{\small II}]$ and $[\rm O{\small III}]$ lines are higher than the average values in local star-forming galaxies and ULIRGs, using the same tracers. From the $[\rm N{\small II}]/[\rm C{\small II}]$ and $[\rm O{\small I}]/[\rm C{\small II}]$ ratios, we find that the $[\rm C{\small II}]$ emission is likely dominated by the photo-dominated regions (PDR), instead of by ionised gas or large-scale shocks.

[60] arXiv:1807.07076v1 [pdf, vox]

Cosmological information in the redshift-space bispectrum

Victoria Yankelevich, Cristiano Porciani
Submitted Wednesday 18 July 2018 @ 18:00:01 GMT
22 pages, 14 figures, comments welcome

We use the Fisher-matrix formalism to investigate whether the galaxy bispectrum in redshift space, $B$, contains additional cosmological information with respect to the power spectrum, $P$. We focus on a $\rm \textit{Euclid}$-lik​e survey and consider cosmological models dominated by dark energy and cold dark matter with Gaussian primordial perturbations. After discussing the phenomenology of redshift-space distortions for the bispectrum, we derive an expression for the cross-covariance between $B$ and $P$ at leading order in perturbation theory. Our equation generalizes previous results that did not consider binning in the orientation of wavevector triangles with respect to the line of sight. By considering Fourier modes with wavenumber $k<0.15 \,h$ Mpc$^{-1}$, we find that $B$ and $P$ set similar constraints on the cosmological parameters. Generally, error bars only moderately improve when the two probes are combined together. The parameters that describe a dynamical dark-energy equation of state, however, form an interesting exception: their joint 68.3 per cent credible region shrinks by a factor of 2.6 with respect to only using the power spectrum. Regrettably, this improvement is canceled out when the clustering analysis is combined with priors based on current studies of the cosmic microwave background. In this case, combining $B$ and $P$ does not give any appreciable benefit other than allowing a precise determination of galaxy bias. Finally, we discuss how results depend on the binning strategy for the clustering statistics as well as on the maximum wavenumber. We also show that only considering the bispectrum monopole leads to a significant loss of information.

[61] arXiv:1807.07077v1 [pdf, vox]

Theory of multiple-stellar population synthesis in a non-Hamiltonian setting

S. Pasetto, D. Crnojević, G. Busso, C. Chiosi, L. P. Cassarà
Submitted Wednesday 18 July 2018 @ 18:00:01 GMT
Accepted for publication on New Astronomy; 15 pages, 2 figures

We aim to investigate the connections existing between the density profiles of the stellar populations used to define a gravitationally bound stellar system and their star formation history: we do this by developing a general framework accounting for both classical stellar population theory and classical stellar dynamics. We extend the work of Pasetto et al. (2012) on a single composite-stellar population (CSP) to multiple CSPs, including also a phase-space description of the CSP concept. In this framework, we use the concept of distribution function to define the CSP in terms of mass, metallicity, and phase-space in a suitable space of existence $\mathbb{E}$ of the CSP. We introduce the concept of foliation of $\mathbb{E}$ to describe formally any CSP as sum of disjointed Simple Stellar Populations (SSP), with the aim to offer a more general formal setting to cast the equations of stellar populations theory and stellar dynamics theory. In doing so, we allow the CSP to be object of dissipation processes thus developing its dynamics in a general non-Hamiltonian framework. Furthermore, we investigate the necessary and sufficient condition to realize a multiple CSP consistent with its mass-metallicity and phase-space distribution function over its temporal evolution, for a collisionless CSP. Finally, analytical and numerical examples show the potential of the result obtained.

[62] arXiv:1807.07069v1 [pdf, vox]

A Deficit of Dark Matter from Jeans Modeling of the Ultra-diffuse Galaxy NGC 1052-DF2

Asher Wasserman, Aaron J. Romanowsky, Jean Brodie, Pieter van Dokkum, Charlie Conroy, Roberto Abraham, Yotam Cohen, Shany Danieli
Submitted Wednesday 18 July 2018 @ 18:00:00 GMT
Submitted to ApJ Letter, version posted is after the initial referee report

The discovery of the ultra-diffuse galaxy NGC 1052-DF2 and its peculiar population of star clusters has raised new questions about the connections between galaxies and dark matter halos at the extremes of galaxy formation. In light of debates over the measured velocity dispersion of its star clusters and the associated mass estimate, we constrain mass models of DF2 using its observed kinematics with a range of priors on the halo mass. Models in which the galaxy obeys a standard stellar-halo mass relation are in tension with the data and also require a large central density core. Better fits are obtained when the halo mass is left free, even after accounting for increased model complexity. The dynamical mass-to-light ratio for our model with a weak prior on the halo mass is $1.7^{+0.7}_{-0.5} \ M_\odot / L_{\odot, V}$, consistent with the stellar population estimate for DF2. We use tidal analysis to find that the low-mass models are consistent with the undisturbed isophotes of DF2. Finally we compare with Local Group dwarf galaxies and demonstrate that DF2 is an outlier in both its spatial extent and its relative dark matter deficit.

[63] arXiv:1807.07070v1 [pdf, vox]

Collective neutrino oscillations with the halo effect in single-angle approximation

Vincenzo Cirigliano, Mark Paris, Shashank Shalgar
Submitted Wednesday 18 July 2018 @ 18:00:00 GMT
13 pages, 5 figures

We perform a self-consistent calculation of collective neutrino oscillations including the effect of back scattered neutrinos (Halo effect) in the `single-angle' approximation, within a spherically symmetric supernova model. We find that due to the Halo effect the onset of flavor transformations is pushed to smaller radii, by a few kilometers. The celebrated phenomenon of the spectral split is found to be robust under the present inclusion of the Halo effect.

[64] arXiv:1807.07072v1 [pdf, vox]

Modeling projection effects in optically-selected cluster catalogues

M. Costanzi, E. Rozo, E. S. Rykoff, A. Farahi, T. Jeltema, A. E. Evrard, A. Mantz, D. Gruen, R. Mandelbaum, J. DeRose, T. McClintock, T. N. Varga, Y. Zhang, J. Weller, R. H. Wechsler, M. Aguena
Submitted Wednesday 18 July 2018 @ 18:00:00 GMT
16 pages, 11 figures

The cosmological utility of galaxy cluster catalogues is primarily limited by our ability to calibrate the relation between halo mass and observable mass proxies such as cluster richness, X-ray luminosity or the Sunyaev-Zeldovich signal. Projection effects are a particularly pernicious systematic effect that can impact observable mass proxies; structure along the line of sight can both bias and increase the scatter of the observable mass proxies used in cluster abundance studies. In this work, we develop an empirical method to characterize the impact of projection effects on redMaPPer cluster catalogues. We use numerical simulations to validate our method and illustrate its robustness. We demonstrate that modeling of projection effects is a necessary component for cluster abundance studies capable of reaching $\approx 5\%$ mass calibration uncertainties (e.g. the Dark Energy Survey Year 1 sample). Specifically, ignoring the impact of projection effects in the observable--mass relation --- i.e. marginalizing over a log-normal model only --- biases the posterior of the cluster normalization condition $S_8 \equiv \sigma_8 (\Omega_{\rm m}/0.3)^{1/2}$ by $\Delta S_8 =0.05$, more than twice the uncertainty in the posterior for such an analysis.

[65] arXiv:1807.07073v1 [pdf, vox]

A sextet of clusters in the Vela OB2 region revealed by Gaia

Giacomo Beccari, Henri M. J. Boffin, Tereza Jerabkova, Nicholas J. Wright, Venu M. Kalari, Giovanni Carraro, Guido De Marchi, Willem-Jan de Wit
Submitted Wednesday 18 July 2018 @ 18:00:00 GMT
Accepted for publication as MNRAS letter. 5 pages and 2 figures

Using Gaia DR2 data, combined with OmegaCAM ground-based optical photometry from the AD-HOC survey, and detailed Radial Velocity measurements from ESO-Gaia, we analyse in detail a 10x5 deg region around the Wolf-Rayet star $\gamma^2$ Vel, including the previously known clusters Gamma Vel and NGC2547. Using clustering analysis that considers positions, proper motions and parallax, we discover 6 clusters or associations -- 4 of which appear new. Analysis of the colour-magnitude diagram for these clusters show that 4 of them formed coevally from the same molecular clouds 10 Myr ago, while NGC 2547 formed together with a newly discovered cluster 30 Myr ago. This study shows the incredible wealth of data provided by Gaia for the study of young stellar clusters.

[66] arXiv:1807.07074v1 [pdf, vox]

The Molecular and Ionized Gas Phases of an AGN-driven Outflow in a Typical Massive Galaxy at z=2

R. Herrera-Camus, L. J. Tacconi, R. Genzel, N. M. Foerster Schreiber, D. Lutz, A. D. Bolatto, S. Wuyts, A. Renzini, S. J. Lilly, S. Belli, H. Uebler, T. Shimizu, R. Davies, E. Sturm, F. Combes, J. Freundlich, S. Garcia-Burillo, P. Cox, A. Burkert, T. Naab, L. Colina, A. Saintonge, M. Cooper, C. Feruglio, A. Weiss
Submitted Wednesday 18 July 2018 @ 18:00:00 GMT
20 pages, 14 figures. Submitted to ApJ

Nuclear outflows driven by accreting massive black holes are one of the main feedback mechanisms invoked at high-z to reproduce the distinct separation between star-forming, disk galaxies and quiescent spheroidal systems. Yet, our knowledge of feedback at high-z remains limited by the lack of observations of the multiple gas phases in galaxy outflows. In this work we use new deep, high-spatial resolution ALMA CO(3-2) and archival VLT/SINFONI H$\alpha$ observations to study the molecular and ionized components of the AGN-driven outflow in zC400528 ---a massive, main sequence galaxy at z=2.3 in the process of quenching. We detect a powerful molecular outflow that shows a positive velocity gradient and extends for at least ~10 kpc from the nuclear region, about three times the projected size of the ionized wind. The molecular gas in the outflow does not reach velocities high enough to escape the galaxy and is therefore expected to be reaccreted. Keeping in mind the various assumptions involved in the analysis, we find that the mass and energetics of the outflow are dominated by the molecular phase. The AGN-driven outflow in zC400528 is powerful enough to deplete the molecular gas reservoir on a timescale at least twice shorter than that needed to exhaust it by star formation. This suggests that the nuclear outflow is one of the main quenching engines at work in the observed suppression of the central star-formation activity in zC400528.

[67] arXiv:1807.07043v1 [pdf, vox]

Review of high-contrast imaging systems for current and future ground-based and space-based telescopes II. Common path wavefront sensing/control and Coherent Differential Imaging

Nemanja Jovanovic, Olivier Absil, Pierre Baudoz, Mathilde Beaulieu, Michael Bottom, Eric Cady, Brunella Carlomagno, Alexis Carlotti, David Doelman, Kevin Fogarty, Raphael Galicher, Olivier Guyon, Sebastiaan Haffert, Elsa Huby, Jeffrey Jewell, Christoph Keller, Matthew A. Kenworthy, Justin Knight, Jonas Kuhn, Kelsey Miller, Johan Mazoyer, Mamadou N'Diaye, Emiel Por, Laurent Pueyo, A J Eldorado Riggs, Garreth Ruane, Dan Sirbu, Frans Snik, J. Kent Wallace, Michael Wilby, Marie Ygouf
Submitted Wednesday 18 July 2018 @ 17:09:07 GMT
18 pages, 9 figures

The Optimal Optical Coronagraph (OOC) Workshop held at the Lorentz Center in September 2017 in Leiden, the Netherlands, gathered a diverse group of 25 researchers working on exoplanet instrumentation to stimulate the emergence and sharing of new ideas. In this second installment of a series of three papers summarizing the outcomes of the OOC workshop (see also~\citenum{ruane2​018,snik2018}), we present an overview of common path wavefront sensing/control and Coherent Differential Imaging techniques, highlight the latest results, and expose their relative strengths and weaknesses. We layout critical milestones for the field with the aim of enhancing future ground/space based high contrast imaging platforms. Techniques like these will help to bridge the daunting contrast gap required to image a terrestrial planet in the zone where it can retain liquid water, in reflected light around a G type star from space.

[68] arXiv:1807.07042v1 [pdf, vox]

Review of high-contrast imaging systems for current and future ground- and space-based telescopes I. Coronagraph design methods and optical performance metrics

G. Ruane, A. Riggs, J. Mazoyer, E. H. Por, M. N'Diaye, E. Huby, P. Baudoz, R. Galicher, E. Douglas, J. Knight, B. Carlomagno, K. Fogarty, L. Pueyo, N. Zimmerman, O. Absil, M. Beaulieu, E. Cady, A. Carlotti, D. Doelman, O. Guyon, S. Haffert, J. Jewell, N. Jovanovic, C. Keller, M. A. Kenworthy, J. Kühn, K. Miller, D. Sirbu, F. Snik, J. Kent Wallace, M. Wilby, M. Ygouf
Submitted Wednesday 18 July 2018 @ 17:04:31 GMT
To appear in Proceedings of the SPIE, vol. 10698

The Optimal Optical Coronagraph (OOC) Workshop at the Lorentz Center in September 2017 in Leiden, the Netherlands gathered a diverse group of 25 researchers working on exoplanet instrumentation to stimulate the emergence and sharing of new ideas. In this first installment of a series of three papers summarizing the outcomes of the OOC workshop, we present an overview of design methods and optical performance metrics developed for coronagraph instruments. The design and optimization of coronagraphs for future telescopes has progressed rapidly over the past several years in the context of space mission studies for Exo-C, WFIRST, HabEx, and LUVOIR as well as ground-based telescopes. Design tools have been developed at several institutions to optimize a variety of coronagraph mask types. We aim to give a broad overview of the approaches used, examples of their utility, and provide the optimization tools to the community. Though it is clear that the basic function of coronagraphs is to suppress starlight while maintaining light from off-axis sources, our community lacks a general set of standard performance metrics that apply to both detecting and characterizing exoplanets. The attendees of the OOC workshop agreed that it would benefit our community to clearly define quantities for comparing the performance of coronagraph designs and systems. Therefore, we also present a set of metrics that may be applied to theoretical designs, testbeds, and deployed instruments. We show how these quantities may be used to easily relate the basic properties of the optical instrument to the detection significance of the given point source in the presence of realistic noise.

[69] arXiv:1807.07037v1 [pdf, vox]

Gravitational wave forest from string axiverse

Naoya Kitajima, Jiro Soda, Yuko Urakawa
Submitted Wednesday 18 July 2018 @ 16:55:57 GMT
27 pages, 16 figures

Axions predicted in string theory may have a scalar potential which has a much shallower potential region than the conventional cosine potential. We first show that axions which were located at such shallow potential regions generically undergo prominent resonance instabilities: the well-known narrow resonance and/or the flapping resonance, which has not been well investigated. We also study non-linear dynamics of axions caused by these resonance instabilities based on lattice simulation. We find that string axions in various mass ranges generate gravitational waves (GWs) with peaks at various frequencies determined by the mass scales, dubbed the GW forest. This may allow us to explore string axiverse through future multi-frequency GW observations. We also investigate GWs produced by the axion which accounts for present dark matter component.

[70] arXiv:1807.06017v2 [pdf, vox]

Chemo-kinematic ages of eccentric-planet-hos​ting M dwarf stars

Mark J. Veyette, Philip S. Muirhead
Submitted Wednesday 18 July 2018 @ 16:38:02 GMT
accepted for publication in ApJ

M dwarf stars are exciting targets for exoplanet investigations; however, their fundamental stellar properties are difficult to measure. Perhaps the most challenging property to measure is stellar age. Once on the main sequence, M dwarfs change imperceptibly in their temperature and luminosity, necessitating novel statistical techniques for estimating their ages. In this paper, we infer ages for known eccentric-planet-hos​ting M dwarfs using a combination of kinematics and $\alpha$-element-enr​ichment, both shown to correlate with age for Sun-like FGK stars. We calibrate our method on FGK stars in a Bayesian context. To measure $\alpha$-enrichment, we use publicly-available spectra from the CARMENES exoplanet survey and a recently developed [Ti/Fe] calibration utilizing individual Ti I and Fe I absorption lines in $Y$ band. Tidal effects are expected to circularize the orbits of short-period planets on short timescales; however, we find a number of mildly eccentric, close-in planets orbiting old ($\sim$8 Gyr) stars. For these systems, we use our ages to constrain the tidal dissipation parameter of the planets, $Q_\mathrm{p}$. For two mini-Neptune planets, GJ 176b and GJ 536b, we find they have $Q_\mathrm{p}$ values more similar to the ice giants than the terrestrial planets in our Solar System. For GJ 436b, we estimate an age of $8.9^{+2.3}_{-2.1}$ Gyr and constrain the $Q_\mathrm{p}$ to be $>10^5$, in good agreement with constraints from its inferred tidal heating. We find that GJ 876d has likely undergone significant orbital evolution over its $8.4^{+2.2}_{-2.0}$ Gyr lifetime, potentially influenced by its three outer companions which orbit in a Laplace resonance.

[71] arXiv:1807.07027v1 [pdf, vox]

Molecular gas filamentary structures in galaxy clusters

Francoise Combes
Submitted Wednesday 18 July 2018 @ 16:30:01 GMT
8 pages, 4 figures, in IAU-S342 -- Perseus in Sicily: from black hole to cluster outskirts -- K. Asada, E. de Gouveia dal Pino, H. Nagai, R. Nemmen, M. Giroletti, eds

Recent molecular line observations with ALMA and NOEMA in several Brightest Cluster Galaxies (BCG) have revealed the large-scale filamentary structure at the center of cool core clusters. These filaments extend over 20-100kpc, they are tightly correlated with ionized gas (H$\alpha$, [NII]) emission, and have characteristic shapes: either radial and straight, or also showing a U-turn, like a horse-shoe structure. The kinematics is quite regular and laminar, and the derived infall time is much longer than the free-fall time. The filaments extend up to the radius where the cooling time becomes larger than the infall time. Filaments can be perturbed by the sloshing of the BCG in its cluster, and spectacular cooling wakes have been observed. Filaments tend to occur at the border of cavities driven in the X-ray gas by the AGN radio jets. Observations of cool core clusters support the thermal instability scenario, which accounts for the multiphase medium in the upper atmospheres of BCG, where the right balance between heating and cooling is reached, and a chaotic cold gas accretion occurs. Molecular filaments are also seen associated to ram-pressure stripped spiral galaxies in rich galaxy clusters, and in jet-induced star formation, suggesting a very efficient molecular cloud formation even in hostile cluster environments.

[72] arXiv:1807.07020v1 [pdf, vox]

High-contrast spectroscopy testbed for Segmented Telescopes: instrument overview and development progress

N. Jovanovic, G. Ruane, D. Echeverri, J. R. Delorme, D. Mawet, J. Fucik, J. K. Wallace, C. Coker, A. Delacroix, N. Levraud, J. D. ~Llop~Sayson, J. Wang, R. Riddle, M. A. Millar-Blanchaer
Submitted Wednesday 18 July 2018 @ 16:14:12 GMT
8 pages, 5 figures

The High Contrast spectroscopy testbed for Segmented Telescopes (HCST) is being developed at Caltech. It aims at addressing the technology gap for future exoplanet imagers and providing the U.S. community with an academic facility to test components and techniques for high contrast imaging, focusing on segmented apertures proposed for future ground-based (TMT, ELT) and space-based telescopes (HabEx, LUVOIR). We present an overview of the design of the instrument and a detailed look at the testbed build and initial alignment. We offer insights into stumbling blocks encountered along the path and show that the testbed is now operational and open for business. We aim to use the testbed in the future for testing of high contrast imaging techniques and technologies with amongst with thing, a TMT-like pupil.

[73] arXiv:1807.07016v1 [pdf, vox]

Testing the ABS method with the simulated Planck temperature maps

Jian Yao, Le Zhang, Yuxi Zhao, Pengjie Zhang, Larissa Santos, Jun Zhang
Submitted Wednesday 18 July 2018 @ 16:04:52 GMT
12 pages, 11 figures

In this study, we apply the Analytical method of Blind Separation (ABS) of the cosmic microwave background (CMB) from foregrounds to estimate the CMB temperature power spectrum from multi-frequency microwave maps. We test the robustness of the ABS estimator and assess the accuracy of the power spectrum recovery by using realistic simulations based on the seven-frequency Planck data, including various frequency-dependent and spatially-varying foreground components (synchrotron, free-free, thermal dust and anomalous microwave emission), as well as an uncorrelated Gaussian-distributed instrumental noise. Considering no prior information about the foregrounds, the ABS estimator can analytically recover the CMB power spectrum over almost all scales with less than $0.5\%$ error for maps where the Galactic plane region ($|b|<10^{\circ}$) is masked out. To further test the flexibility and effectiveness of the ABS approach in a variety of situations, we apply the ABS to the simulated Planck maps in three cases: (1) without any mask, (2) imposing a two-times-stronger synchrotron emission and (3) including only the Galactic plane region ($|b|<10^{\circ}$) in the analysis. In such extreme cases, the ABS approach can still provide an unbiased estimate of band powers at the level of 1 $\mu\rm{K}^2$ on average over all $\ell$ range, and the recovered powers are consistent with the input values within 1-$\sigma$ for most $\ell$ bins.

[74] arXiv:1807.07010v1 [pdf, vox]

GRAPE: Genetic Routine for Astronomical Period Estimation

Paul R. McWhirter, Iain A. Steele, Abir Hussain, Dhiya Al-Jumeily, Marley M. B. R. Vellasco
Submitted Wednesday 18 July 2018 @ 15:57:39 GMT
18 pages, 21 figures, 10 tables, accepted to MNRAS

Period estimation is an important task in the classification of many variable astrophysical objects. Here we present GRAPE: Genetic Routine for Astronomical Period Estimation, a genetic algorithm optimised for the processing of survey data with spurious and aliased artefacts. It uses a Bayesian Generalised Lomb-Scargle (BGLS) fitness function designed for use with the Skycam survey conducted at the Liverpool Telescope. We construct a set of simulated light curves using both regular and Skycam survey cadence with four types of signal: sinusoidal, sawtooth, symmetric eclipsing binary and eccentric eclipsing binary. We apply GRAPE and a BGLS periodogram to this data and show that the performance of GRAPE is superior to the periodogram on sinusoidal and sawtooth light curves with relative hit rate improvement of 18.2% and 6.4% respectively. The symmetric and eccentric eclipsing binary light curves have similar performance on both methods. We show the Skycam cadence is sufficient to correctly estimate the period for all of the sinusoidal shape light curves although this degrades with increased non-sinusoidal shape with sawtooth, symmetric binary and eccentric binary light curves down by 20%, 30% and 35% respectively. The runtime of GRAPE demonstrates that light curves with more than 500-1000 data points achieve similar performance in less computing time. The GRAPE performance can be matched by a frequency spectrum with an oversampled fine-tuning grid at the cost of almost doubling the runtime. Finally, we propose improvements which will extend this method to the detection of quasi-periodic signals and the use of multiband light curves.

[75] arXiv:1807.07427v1 [pdf, vox]

Implications of dedicated seismometer measurements on Newtonian-noise cancellation for Advanced LIGO

M. W. Coughlin, J. Harms, J. Driggers, D. J. McManus, N. Mukund, M. P. Ross, B. J. J. Slagmolen, K. Venkateswara
Submitted Wednesday 18 July 2018 @ 15:49:36 GMT

Newtonian gravitational noise from seismic fields will become a limiting noise source at low frequency for second-generation, gravitational-wave detectors. It is planned to use seismic sensors surrounding the detectors' test masses to coherently subtract Newtonian noise using Wiener filters derived from the correlations between the sensors and detector data. In this work, we use data from a seismometer array deployed at the corner station of the LIGO Hanford detector combined with a tiltmeter for a detailed characterization of the seismic field and to predict achievable Newtonian-noise subtraction levels. As was shown previously, cancellation of the tiltmeter signal using seismometer data serves as the best available proxy of Newtonian-noise cancellation. According to our results, a relatively small number of seismometers is likely sufficient to perform the noise cancellation due to an almost ideal two-point spatial correlation of seismic surface displacement at the corner station, or alternatively, a tiltmeter deployed under each of the two test masses of the corner station at Hanford will be able to efficiently cancel Newtonian noise. Furthermore, we show that the ground tilt to differential arm-length coupling observed during LIGO's second science run is consistent with gravitational coupling.

[76] arXiv:1807.06995v1 [pdf, vox]

Optical dimming of RW Aur associated with an iron rich corona and exceptionally high absorbing column density

Hans Moritz Günther, T. Birnstiel, D. P. Huenemoerder, D. A. Principe, P. C. Schneider, S. J. Wolk, Franky Dubois, Ludwig Logie, Steve Rau, Sigfried Vanaverbeke
Submitted Wednesday 18 July 2018 @ 15:32:31 GMT
accepted by AJ

RW Aur is a binary system composed of two young, low-mass stars. The primary, RW Aur A, has undergone visual dimming events ($\Delta V =2-3$~mag) in 2011, 2014-16, and 2017-2018. Visual and IR observations indicate a gray absorber that moved into the line-of-sight. This dimming is also associated with changes in the outflow. In 2017, when the optical brightness was almost 2~mag below the long-term average we triggered a Chandra observation to measure the absorbing column density $N_\mathrm{H}$ and to constrain dust properties and the gas-to-dust ratio of the absorber. In 2017, the X-ray spectrum is more absorbed than it was in the optically bright state ($N_\mathrm{H} = (4\pm 1) \times 10^{23}\;\mathrm{cm}​^{-2}$) and shows significantly more hot plasma than in X-ray observations taken before. Also, a new emission feature at $6.63\pm0.02$ keV (statistic) $\pm0.02$ keV (systematic) appeared indicating an Fe abundance an order of magnitude above Solar, in contrast with previous sub-Solar Fe abundance measurements. Comparing X-ray absorbing column density $N_\mathrm{H}$ and optical extinction $A_V$, we find that either the gas-to-dust ratio in the absorber is orders of magnitude higher than in the ISM or the absorber has undergone significant dust evolution. Given the high column density coupled with changes in the X-ray spectral shape, this absorber is probably located in the inner disk. We speculate that a break-up of planetesimals or a terrestrial planet could supply large grains causing gray absorption; some of these grains would be accreted and enrich the stellar corona with iron which could explain the inferred high abundance.

[77] arXiv:1807.06989v1 [pdf, vox]

Observations of Low-Frequency Radio Emission from Millisecond Pulsars and Multipath Propagation in the Interstellar Medium

N. D. R. Bhat, S. E. Tremblay, F. Kirsten, B. W. Meyers, M. Sokolowski, W. van Straten, S. J. McSweeney, S. M. Ord, R. M. Shannon, A. Beardsley, B. Crosse, D. Emrich, T. M. O. Franzen, L. Horsley, M. Johnston-Hollitt, D. L. Kaplan, D. Kenney, M. F. Morales, D. Pallot, K. Steele, S. J. Tingay, C. M. Trott, M. Walker, R. B. Wayth, A. Williams, C. Wu
Submitted Wednesday 18 July 2018 @ 15:11:37 GMT
23 pages, 10 Figures, 4 Tables, Accepted to ApJS

Studying the gravitational-wave sky with pulsar timing arrays (PTAs) is a key science goal for the Square Kilometre Array (SKA) and its pathfinder telescopes. With current PTAs reaching sub-microsecond timing precision, making accurate measurements of interstellar propagation effects and mitigating them effectively has become increasingly important to realise PTA goals. As these effects are much stronger at longer wavelengths, low-frequency observations are most appealing for characterizing the interstellar medium (ISM) along the sight lines toward PTA pulsars. The Murchison Widefield Array (MWA) and the Engineering Development Array (EDA), which utilizes MWA technologies, present promising opportunities for undertaking such studies, particularly for PTA pulsars located in the southern sky. Such pulsars are also the prime targets for PTA efforts planned with the South African MeerKAT, and eventually with the SKA. In this paper we report on observations of two bright southern millisecond pulsars PSRs J0437-4715 and J2145-0750 made with these facilities; MWA observations sampling multiple frequencies across the 80-250 MHz frequency range, while the EDA providing direct-sampled baseband data to yield a large instantaneous usable bandwidth of $\sim$200 MHz. Using these observations, we investigate various aspects relating to pulsar emission and ISM properties, such as spectral evolution of the mean pulse shape, scintillation as a function of frequency, chromaticity in interstellar dispersion, and flux density spectra at low frequencies. Systematic and regular monitoring observations will help ascertain the role of low-frequency measurements in PTA experiments, while simultaneously providing a detailed characterization of the ISM toward the pulsars, which will be useful in devising optimal observing strategies for future PTA experiments.

[78] arXiv:1807.06984v1 [pdf, vox]

Correlations between radio and bolometric fluxes in GX 339-4 and H1743-322

Nazma Islam, Andrzej A. Zdziarski
Submitted Wednesday 18 July 2018 @ 15:00:03 GMT
submitted to MNRAS, 8 pages

Compact radio jets are ubiquitous in stellar-mass black-hole binaries in their hard spectral state. Empirical relations between the radio and narrow-band X-ray fluxes have been used to understand the connection between their accretion discs and jets. However, a narrow-band (e.g., 1--10 or 3--9 keV) X-ray flux can be a poor proxy for either the bolometric luminosity or the mass accretion rate. Here, we study correlations between the radio and unabsorbed broad-band X-ray fluxes, the latter providing good estimates of the bolometric flux. We consider GX 339--4, the benchmark object for the main branch of the correlation, and H1743--322, the first source found to be an outlier of the correlation. The obtained power-law dependencies of the radio flux on the bolometric flux have significantly different indices from those found for the narrow X-ray bands. Also, the radio/bolometric flux correlations for the rise of the outbursts are found to be significantly different from those for the outburst decline. This points to a possible existence of a jet hysteresis in the radio/X-ray source evolution, in addition to that seen in the hardness/flux diagram of low-mass X-ray binaries. The correlation during the rise of the outbursts is similar for both GX 339--4 and H1743--322. The correlation for the decline of the outbursts for H1743--322 lies below that of GX 339--4 at intermediate X-ray fluxes, whereas it approaches the standard correlation at lower X-ray luminosities. We also compare these correlations to those for the high-mass X-ray binaries Cyg X-1 and Cyg X-3.

[79] arXiv:1807.06974v1 [pdf, vox]

Non standard s-process in massive rotating stars. Yields of $10-150$ $M_{\odot}$ models at $Z=10^{-3}$

Arthur Choplin, Raphael Hirschi, Georges Meynet, Sylvia Ekstroöm, Cristina Chiappini, Alison Laird
Submitted Wednesday 18 July 2018 @ 14:35:29 GMT
16 pages, 14 figures, 4 tables. Accepted for publication in A&A

Recent studies show that rotation significantly affects the s-process in massive stars. We provide tables of yields for non-rotating and rotating massive stars between 10 and 150 $M_{\odot}$ at $Z=10^{-3}$ ([Fe/H] $=-1.8$). Tables for different mass cuts are provided. The complete s-process is followed during the whole evolution with a network of 737 isotopes, from Hydrogen to Polonium. A grid of stellar models with initial masses of 10, 15, 20, 25, 40, 60, 85, 120 and 150 $M_{\odot}$ and with an initial rotation rate of both 0 or 40$~\%$ of the critical velocity was computed. Three extra models were computed in order to investigate the effect of faster rotation (70$~\%$ of the critical velocity) and of a lower $^{17}$O($\alpha,\ga​mma$) reaction rate. At the considered metallicity, rotation has a strong impact on the production of s-elements for initial masses between 20 and 60 $M_{\odot}$. In this range, the first s-process peak is boosted by $2-3$ dex if rotation is included. Above 60 $M_{\odot}$, s-element yields of rotating and non-rotating models are similar. Increasing the initial rotation from 40$~\%$ to 70$~\%$ of the critical velocity enhances the production of $40 \lesssim Z \lesssim 60$ elements by $\sim 0.5-1$ dex. Adopting a reasonably lower $^{17}$O($\alpha,\ga​mma$) rate in the fast rotating model (70$~\%$ of the critical velocity) boosts again the yields of s-elements with $55 \lesssim Z \lesssim 82$ by about 1 dex. In particular, a modest amount of Pb is produced. Together with s-elements, some light elements (particularly fluorine) are strongly overproduced in rotating models.

[80] arXiv:1807.06973v1 [pdf, vox]

WASP-147b, 160Bb, 164b and 165b: two hot Saturns and two Jupiters, including two planets with metal-rich hosts

M. Lendl, D. R. Anderson, A. Bonfanti, F. Bouchy, A. Burdanov, A. Collier Cameron, L. Delrez, M. Gillon, C. Hellier, E. Jehin, P. F. L. Maxted, L. Dyregaard Nielsen, F. Pepe, D. Pollacco, D. Queloz, D. Segransan, J. Southworth, B. Smalley, S. Thompson, O. Turner, A. H. M. J. Triaud, S. Udry, R. G. West
Submitted Wednesday 18 July 2018 @ 14:34:34 GMT
Submitted to MNRAS

We report the discovery of four transiting hot Jupiters, WASP-147, WASP-160B, WASP-164 and WASP-165 from the WASP survey. WASP-147b is a near Saturn-mass ($M_P = 0.28 M_{J}$) object with a radius of $ 1.11 \, R_{J}$ orbiting a G4 star with a period of $ 4.6 $~d. WASP-160Bb has a mass and radius ($ M_p = 0.28 \, M_J $, $ R_p = 1.09 \, R_J$) near-identical to WASP-147b, but is less irradiated, orbiting a metal-rich K0 star with a period of $3.8$~d. WASP-160B is part of a near equal-mass visual binary with an on-sky separation of 28.5~arcsec. WASP-164b is a more massive ($M_P = 2.13 \, M_J$, $R_p = 1.13 \, R_J$) hot Jupiter, orbiting a G2 star on a close-in ($P=1.8$~d), but tidally stable orbit. WASP-165b is a classical ($M_p = 0.66 \, M_J$, $R_P = 1.26 \, R_J$) hot Jupiter in a $3.5$~d period orbit around a metal-rich star. WASP-160B and WASP-165 are two of the most metal-rich stars ($\mathrm{[Fe/H]}_{\​ast}=0.389\pm0.080$ and $0.33\pm0.13$, respectively) known to host a transiting hot Jupiter. WASP-147b and WASP-160Bb are promising targets for atmospheric characterization through transmission spectroscopy, while WASP-164b presents a good target for emission spectroscopy.

[81] arXiv:1807.06959v1 [pdf, vox]

Full 3D Numerical Relativity Simulations of Neutron Star -- Boson Star Collisions with BAM

Tim Dietrich, Serguei Ossokine, Katy Clough
Submitted Wednesday 18 July 2018 @ 14:22:20 GMT

With the first direct detections of gravitational waves (GWs) from the coalescence of compact binaries observed by the advanced LIGO and VIRGO interferometers, the era of GW astronomy has begun. Whilst there is strong evidence that the observed GWs are connected to the merger of two black holes (BH) or two neutron stars (NS), future detections may present a less consistent picture. Indeed, the possibility that the observed GW signal was created by a merger of exotic compact objects (ECOs) such as boson stars (BS) or axion stars (AS) has not yet been fully excluded. For a detailed understanding of the late stages of the coalescence full 3D numerical relativity simulations are essential. In this paper, we extend the infrastructure of the numerical relativity code BAM, to permit the simultaneous simulation of baryonic matter with bosonic scalar fields, thus enabling the study of BS-BS, BS-NS, and BS-BH mergers. We present a large number of single star evolutions to test the newly implemented routines, and to quantify the numerical challenges of such simulations, which we find to partially differ from the default NS case. We also compare head-on BS-BS simulations with independent numerical relativity codes, namely the SpEC and the GRChombo codes, and find good general agreement. Finally, we present what are, to the best of our knowledge, the first full NR simulations of BS-NS mergers, a first step towards identifying the hallmarks of BS-NS interactions in the strong gravity regime, as well as possible GW and electromagnetic observables.

[82] arXiv:1807.07477v1 [pdf, vox]

Enhancing the cross-correlations between magnetic fields and scalar perturbations through parity violation

Debika Chowdhury, L. Sriramkumar, Marc Kamionkowski
Submitted Wednesday 18 July 2018 @ 14:19:39 GMT
20 pages, 4 figures. arXiv admin note: text overlap with arXiv:1807.05530

One often resorts to a non-minimal coupling of the electromagnetic field in order to generate magnetic fields during inflation. The coupling is expected to depend on a scalar field, possibly the same as the one driving inflation. At the level of three-point functions, such a coupling leads to a non-trivial cross-correlation between the perturbation in the scalar field and the magnetic field. This cross-correlation has been evaluated analytically earlier for the case of non-helical electromagnetic fields. In this work, we numerically compute the cross-correlation for helical magnetic fields. Non-Gaussianities are often generated as modes leave the Hubble radius. The helical electromagnetic modes evolve strongly (when compared to the non-helical case) around Hubble exit and one type of polarization is strongly amplified immediately after Hubble exit. We find that helicity considerably boosts the amplitude of the dimensionless non-Gaussianity parameter that characterizes the amplitude and shape of the cross-correlation between the perturbations in the scalar field and the magnetic field. We discuss the implications of the enhancement in the non-Gaussianity parameter due to parity violation.

[83] arXiv:1807.06954v1 [pdf, vox]

Levels of chromospheric and coronal activity in Sun-like stars and various types of dynamo waves

E. A. Bruevich, M. M. Katsova, D. D. Sokolov
Submitted Wednesday 18 July 2018 @ 14:13:27 GMT
22 pages, 5 figures

We analyze the X-ray emission and chromospheric activity of Sun-like stars of F, G and K spectral classes (late-type stars) studied in the framework of the HK project. More powerful coronas are possessed by stars displaying irregular variations of their chromospheric emission, while stars with regular cyclic activity are characterized by comparatively modest X-ray luminosities and ratios of the X-ray to bolometric luminosity. This indicates that the nature of processes associated with magnetic-field amplification on the convective envelope changes appreciably in the transition from small to large dynamo numbers, directly affecting the character of the alpha-Omega dynamo. Due to the strong dependence of both the dynamo number and the Rossby number on the speed of axial rotation, earlier correlations found between various activity parameters and the Rossby number are consistent with our conclusion. Our analysis makes it possible to draw the first firm conclusions about the place of solar activity among analogous processes developing in active late-type stars.

[84] arXiv:1807.06423v2 [pdf, vox]

The SAFARI Detector System

Michael D. Audley, Gert de Lange, Jian-Rong Gao, Brian D. Jackson, Richard A. Hijmering, Marcel L. Ridder, Marcel P. Bruijn, Peter R. Roelfsema, Peter A. R. Ade, Stafford Withington, Charles M. Bradford, Neal A. Trappe
Submitted Wednesday 18 July 2018 @ 13:21:24 GMT
7 pages, 3 figures, Proc. SPIE 10708, Millimeter, Submillimeter, and Far-Infrared Detectors and Instrumentation for Astronomy IX, 107080K (9 July 2018); (fixed typo in abstract)

We give an overview of the baseline detector system for SAFARI, the prime focal-plane instrument on board the proposed space infrared observatory, SPICA. SAFARI's detectors are based on superconducting Transition Edge Sensors (TES) to provide the extreme sensitivity (dark NEP$\le2\times10^{-1​9}\rm\ W/\sqrt Hz$) needed to take advantage of SPICA's cold (<8 K) telescope. In order to read out the total of ~3500 detectors we use frequency domain multiplexing (FDM) with baseband feedback. In each multiplexing channel, a two-stage SQUID preamplifier reads out 160 detectors. We describe the detector system and discuss some of the considerations that informed its design.

[85] arXiv:1807.06904v1 [pdf, vox]

Cosmic dance in the Shapley Concentration Core - I. A study of the radio emission of the BCGs and tailed radio galaxies

G. Di Gennaro, T. Venturi, D. Dallacasa, S. Giacintucci, P. Merluzzi, G. Busarello, A. Mercurio, S. Bardelli, F. Gastaldello, A. Grado, C. P. Haines, L. Limatola, M. Rossetti
Submitted Wednesday 18 July 2018 @ 13:06:41 GMT
24 pages, 11 figures, accepted for publication in Astronomy & Astrophysics

The Shapley Concentration ($z\approx0.048$) covers several degrees in the Southern Hemisphere, and includes galaxy clusters in advanced evolutionary stage, groups of clusters in the early stages of merger, fairly massive clusters with ongoing accretion activity, and smaller groups located in filaments in the regions between the main clusters. With the goal to investigate the role of cluster mergers and accretion on the radio galaxy population, we performed a multi-wavelength study of the BCGs and of the galaxies showing extended radio emission in the cluster complexes of Abell 3528 and Abell 3558. Our study is based on a sample of 12 galaxies. We observed the clusters with the GMRT at 235, 325 and 610 MHz, and with the VLA at 8.46 GHz. We complemented our study with the TGSS at 150 MHz, the SUMSS at 843 MHz and ATCA at 1380, 1400, 2380, and 4790 MHz data. Optical imaging with ESO-VST and mid-IR coverage with WISE are also available for the host galaxies. We found deep differences in the properties of the radio emission of the BCGs in the two cluster complexes. The BCGs in the A3528 complex and in A3556, which are relaxed cool-core objects, are powerful active radio galaxies. They also present hints of restarted activity. On the contrary, the BCGs in A3558 and A3562, which are well known merging systems, are very faint, or quiet, in the radio band. The optical and IR properties of the galaxies are fairly similar in the two complexes, showing all passive red galaxies. Our study shows remarkable differences in the radio properties of the BGCs, which we relate to the different dynamical state of the host cluster. On the contrary, the lack of changes between such different environments in the optical band suggests that the dynamical state of galaxy clusters does not affect the optical counterparts of the radio galaxies, at least over the life-time of the radio emission.

[86] arXiv:1807.06903v1 [pdf, vox]

The Hot Universe with XRISM and Athena

Matteo Guainazzi, Makoto S. Tashiro
Submitted Wednesday 18 July 2018 @ 13:04:36 GMT
Proceedings of the IAU Symposium IAUS342, "Perseus in Sicily: from black hole to cluster outskirts". 8 pages, 3 figures

X-ray spectroscopy is key to address the theme of "The Hot Universe", the still poorly understood astrophysical processes driving the cosmological evolution of the baryonic hot gas traceable through its electromagnetic radiation. Two future X-ray observatories: the JAXA-led XRISM (due to launch in the early 2020s), and the ESA Cosmic Vision L-class mission Athena (early 2030s) will provide breakthroughs in our understanding of how and when large-scale hot gas structures formed in the Universe, and in tracking their evolution from the formation epoch to the present day.

[87] arXiv:1807.06902v1 [pdf, vox]

New catalogue of Chemically Peculiar stars, and Statistical Analysis

S. Ghazaryan, G. Alecian, A. A. Hakobyan
Submitted Wednesday 18 July 2018 @ 13:03:51 GMT
12 pages, 5 figures, 4 tables, and online materials

In this paper we present a new catalogue of Chemically Peculiar (CP) stars obtained by compiling publications in which abundances of metals are provided. Our catalogue includes 428 stars for which the data were obtained through spectroscopic observations. Most of them (416) are AmFm, HgMn and ApBp stars. We have used this compilation to proceed to a statistical overview of the abundance anomalies versus the physical parameters of the stars. The Spearman's rank correlation test has been applied, and a significant number of correlations of abundance peculiarities with respect to effective temperature, surface gravity and rotation velocity have been found. Four interesting cases are discussed in details: the Mn peculiarities in HgMn stars, the Ca correlation with respect to effective temperature in AmFm stars, the case of helium and iron in ApBp stars. Furthermore, we checked for ApBp stars using Anderson-Darling test wether the belonging to a multiple system is a determinant parameter or not for abundance peculiarities.

[88] arXiv:1807.06900v1 [pdf, vox]

Two-loop corrections to Starobinsky-Higgs inflation

D. M. Ghilencea
Submitted Wednesday 18 July 2018 @ 12:58:41 GMT
21 pages, 8 figures

Higgs inflation and $R^2$-inflation (Starobinsky model) are two limits of the same quantum model, hereafter called Starobinsky-Higgs. We analyse the two-loop action of the Higgs-like scalar $\phi$ in the presence of: 1) non-minimal coupling ($\xi$) and 2) quadratic curvature terms. The latter are generated at the quantum level with $\phi$-dependent couplings ($\tilde\alpha$) even if their tree-level couplings ($\alpha$) are tuned to zero. Therefore, the potential always depends on both Higgs $\phi$ and scalaron $\rho$, hence multi-field inflation is a quantum consequence. The effects of the quantum (one- and two-loop) corrections on the potential $\hat W(\phi,\rho)$ are discussed, to conclude that the Starobinsky-Higgs model is in general stable in their presence. Two special cases are also considered: first, for a large $\xi$ in the quantum action one can integrate $\phi$ and generate a "refined" Starobinsky model which contains additional terms $\xi^2 R^2\ln^p (\xi \vert R\vert/\mu^2)$, $p=1,2$, ($\mu$ is the subtraction scale). This case generates corrections linear in the scalaron to the "usual" Starobinsky potential and a "running" scalaron mass. Second, for a small (fixed) higgs field $\phi^2 \ll M_p^2/\xi$ and a vanishing classical coefficient of the $R^2$-term, "usual" Starobinsky inflation is generated by quantum corrections for a suitable non-minimal coupling ($\xi$).

[89] arXiv:1807.06880v1 [pdf, vox]

Anti-Gravitating Brane-World Solutions for a de Sitter Brane in Scalar-Tensor Gravity

Panagiota Kanti, Theodoros Nakas, Nikolaos Pappas
Submitted Wednesday 18 July 2018 @ 11:57:03 GMT
29 pages, 8 figures

In the context of a five-dimensional theory with a scalar field non-minimally-couple​d to gravity, we look for solutions that describe novel black-string or maximally-symmetric solutions in the bulk. The brane line-element is found to describe a Schwarzschild-(Anti)​-de Sitter spacetime, and, here, we choose to study solutions with a positive four-dimensional cosmological constant. We consider two different forms of the coupling function of the scalar field to the bulk scalar curvature, a linear and a quadratic one. In the linear case, we find solutions where the theory, close to our brane, mimics an ordinary gravitational theory with a minimally-coupled scalar field giving rise to an exponentially decreasing warp factor in the absence of a negative bulk cosmological constant. The solution is characterised by the presence of a normal gravity regime around our brane and an anti-gravitating regime away from it. In the quadratic case, there is no normal-gravity regime at all, however, scalar field and energy-momentum tensor components are well-defined and an exponentially decreasing warp factor emerges again. We demonstrate that, in the context of this theory, the emergence of a positive cosmological constant on our brane is always accompanied by an anti-gravitating regime in the five-dimensional bulk.

[90] arXiv:1807.06875v1 [pdf, vox]

A Bayesian method for combining theoretical and simulated covariance matrices for large-scale structure surveys

Alex Hall, Andy Taylor
Submitted Wednesday 18 July 2018 @ 11:49:15 GMT
20 pages, 11 figures. Submitted to MNRAS

Accurate and precise covariance matrices will be important in enabling planned cosmological surveys to detect new physics. Standard methods imply either the need for many N-body simulations in order to obtain an accurate estimate, or a precise theoretical model. We combine these approaches by constructing a likelihood function conditioned on simulated and theoretical covariances, consistently propagating noise from the finite number of simulations and uncertainty in the theoretical model itself using an informative Inverse-Wishart prior. Unlike standard methods, our approach allows the required number of simulations to be less than the number of summary statistics. We recover the linear 'shrinkage' covariance estimator in the context of a Bayesian data model, and test our marginal likelihood on simulated mock power spectrum estimates. We conduct a thorough investigation into the impact of prior confidence in different choices of covariance models on the quality of model fits and parameter variances. In a simplified setting we find that the number of simulations required can be reduced if one is willing to accept a mild degradation in the quality of model fits, finding that even weakly informative priors can help to reduce the simulation requirements. We identify the correlation matrix of the summary statistics as a key quantity requiring careful modelling. Our approach can be easily generalized to any covariance model or set of summary statistics, and elucidates the role of hybrid estimators in cosmological inference.

[91] arXiv:1807.06870v1 [pdf, vox]

Detecting Domain Walls in Laboratory Experiments

Claudio Llinares, Philippe Brax
Submitted Wednesday 18 July 2018 @ 11:33:33 GMT
6 pages, 5 figures

The inherently unstable nature of domain walls makes their detection in laboratory experiments extremely challenging. We propose a method to stabilise domain walls in a particular modified gravity model inside a cavity. We suggest two ways in which the walls could be detected once stabilized: studying the trajectories of Ultra Cold Neutrons (UCN's) either via the deflection angle of a neutron beam induced by the attraction towards the wall or through the time difference of these particles passing through the wall. We give realistic estimates for these effects and expect that they should be detectable experimentally.

[92] arXiv:1807.06857v1 [pdf, vox]

Gravitational waves and mass ejecta from binary neutron star mergers: Effect of large eccentricities

Swami Vivekanandji Chaurasia, Tim Dietrich, Nathan K. Johnson-McDaniel, Maximiliano Ujevic, Wolfgang Tichy, Bernd Brügmann
Submitted Wednesday 18 July 2018 @ 10:49:29 GMT
(24 pages, 17 figures), "CoRe webpage, see http://www.computati​onal-relativity.org/​"

As current gravitational wave (GW) detectors increase in sensitivity, and particularly as new instruments are being planned, there is the possibility that ground-based GW detectors will observe GWs from highly eccentric neutron star binaries. We present the first detailed study of highly eccentric BNS systems with full (3+1)D numerical relativity simulations using consistent initial conditions, i.e., setups which are in agreement with the Einstein equations and with the equations of general relativistic hydrodynamics in equilibrium. Overall, our simulations cover two different equations of state (EOSs), two different spin configurations, and three to four different initial eccentricities for each pairing of EOS and spin. We extract from the simulated waveforms the frequency of the f-mode oscillations induced during close encounters before the merger of the two stars. The extracted frequency is in good agreement with f-mode oscillations of individual stars for the irrotational cases, which allows an independent measure of the supranuclear equation of state not accessible for binaries on quasi-circular orbits. The energy stored in these f-mode oscillations can be as large as $10^{-3}M_\odot \sim 10^{51}$ erg, even with a soft EOS. In order to estimate the stored energy, we also examine the effects of mode mixing due to the stars' offset from the origin on the f-mode contribution to the GW signal. While in general (eccentric) neutron star mergers produce bright electromagnetic counterparts, we find that the luminosity decreases when the eccentricity becomes too large, due to a decrease of the ejecta mass. Finally, the use of consistent initial configurations also allows us to produce high-quality waveforms for different eccentricities which can be used as a testbed for waveform model development of highly eccentric binary neutron star systems.

[93] arXiv:1807.06855v1 [pdf, vox]

Afterburst thermal relaxation in neutron star crusts

E. A. Chaikin, A. D. Kaminker, D. G. Yakovlev
Submitted Wednesday 18 July 2018 @ 10:48:43 GMT
15 pages, 10 figures, Astrophysics and Space Science, accepted

We study thermal relaxation in a neutron star after internal heating events (outbursts) in the crust. We consider thin and thick spherically symmetric heaters, superfluid and non-superfluid crusts, stars with open and forbidden direct Urca processes in their cores. In particular, we analyze long-term thermal relaxation after deep crustal heating produced by nuclear transformations in fully or partly accreted crusts of transiently accreting neutron stars. This long-term relaxation has a typical relaxation time and an overall finite duration time for the crust to thermally equilibrate with the core. Neutron superfluidity in the inner crust greatly affects the relaxation if the heater is located in the inner crust. It shortens and unifies the time of emergence of thermal wave from the heater to the surface. This is important for the interpretation of observed outbursts of magnetars and transiently accreting neutron stars in quasi-persistent low-mass X-ray binaries.

[94] arXiv:1807.03946v3 [pdf, vox]

A weak modulation effect detected in the light curves of KIC 5950759: intrinsic or instrumental effect?

Taozhi Yang, A. Esamdin, Fangfang Song, Hubiao Niu, Guojie Feng, Peng Zong, Xiangyun Zeng, Junhui Liu, Jinzhong liu, Lu Ma, Fei Zhao
Submitted Wednesday 18 July 2018 @ 10:43:19 GMT
25 pages, 7 figures. To appear in ApJ

In this paper, the high-precision light curves of $Kepler$ target KIC 5950759 are analyzed. The Fourier analysis of the long cadence light curve reveals 3 independent frequencies. Two of them are main pulsation modes: F0 = 14.221373(21) $\rm{d^{-1}}$ and F1 = 18.337249(44) $\rm{d^{-1}}$. The third independent frequency $f_m$ = 0.3193 d$^{-1}$ is found in long cadence data with a signal-to-noise ratio of 6.2. A weak modulation of $f_m$ to F0 and F1 modes (triplet structures centred on F0 and F1) are detected both in long and short cadence data. This is the first detection of the modulation effect in a double-mode HADS star. The most possible cause of the modulation effect in the light curves is amplitude modulation with the star's rotation frequency of 0.3193 d$^{-1}$. The preliminary analysis suggests that KIC 5950759 is in the bottom of the HADS instability strip and likely situated in the main sequence. Spectroscopic observations are necessary to verify the true nature of the modulation terms.

[95] arXiv:1807.06844v1 [pdf, vox]

Evolution of Earth-like extrasolar planetary atmospheres: Assessing the atmospheres and biospheres of early Earth analog planets with a coupled atmosphere biogeochemical model

S. Gebauer, J. L. Grenfell, J. W. Stock, R. Lehmann, M. Godolt, P. von Paris, H. Rauer
Submitted Wednesday 18 July 2018 @ 10:16:11 GMT
72 pages, 28 figures, 7 tables

Understanding the evolution of Earth and potentially habitable Earth-like worlds is essential to fathom our origin in the Universe. The search for Earth-like planets in the habitable zone and investigation of their atmospheres with climate and photochemical models is a central focus in exoplanetary science. Taking the evolution of Earth as a reference for Earth-like planets, a central scientific goal is to understand what the interactions were between atmosphere, geology, and biology on early Earth. The Great Oxidation Event (GOE) in Earth's history was certainly caused by their interplay, but the origin and controlling processes of this occurrence are not well understood, the study of which will require interdisciplinary, coupled models. In this work, we present results from our newly developed Coupled Atmosphere Biogeochemistry model in which atmospheric O$_2$ concentrations are fixed to values inferred by geological evidence. Applying a unique tool, ours is the first quantitative analysis of catalytic cycles that governed O$_2$ in early Earth's atmosphere near the GOE. Complicated oxidation pathways play a key role in destroying O$_2$, whereas in the upper atmosphere, most O$_2$ is formed abiotically via CO$_2$ photolysis. The O$_2$ bistability found by Goldblatt et al. (2006) is not observed in our calculations likely due to our detailed CH$_4$ oxidation scheme. We calculate increased CH$_4$ with increasing O$_2$ during the GOE. For a given atmospheric surface flux, different atmospheric states are possible; however, the net primary productivity (NPP) of the biosphere that produces O$_2$ is unique. Mixing, CH$_4$ fluxes, ocean solubility, and mantle/crust properties strongly affect NPP and surface O$_2$ fluxes. Regarding exoplanets, different "states" of O$_2$ could exist for similar biomass output. Strong geological activity could lead to false negatives for life.

[96] arXiv:1807.06837v1 [pdf, vox]

High-resolution radio imaging of two luminous quasars beyond redshift 4.5

S. Frey, O. Titov, A. E. Melnikov, P. de Vicente, F. Shu
Submitted Wednesday 18 July 2018 @ 10:02:36 GMT
8 pages, 3 figures, accepted for publication in Astronomy & Astrophysics

Context. Radio-loud active galactic nuclei in the early Universe are rare. The quasars J0906+6930 at redshift z=5.47 and J2102+6015 at z=4.57 stand out from the known sample with their compact emission on milliarcsecond (mas) angular scale with high (0.1-Jy level) flux densities measured at GHz radio frequencies. This makes them ideal targets for very long baseline interferometry (VLBI) observations. Aims. By means of VLBI imaging we can reveal the inner radio structure of quasars and model their brightness distribution to better understand the geometry of the jet and the physics of the sources. Methods. We present sensitive high-resolution VLBI images of J0906+6930 and J2102+6015 at two observing frequencies, 2.3 and 8.6 GHz. The data were taken in an astrometric observing programme involving a global five-element radio telescope array. We combined the data from five different epochs from 2017 February to August. Results. For one of the highest redshift blazars known, J0906+6930, we present the first-ever VLBI image obtained at a frequency below 8 GHz. Based on our images at 2.3 and 8.6 GHz, we confirm that this source has a sharply bent helical inner jet structure within ~3 mas from the core. The quasar J2102+6015 shows an elongated radio structure in the east-west direction within the innermost ~2 mas that can be described with a symmetric three-component brightness distribution model at 8.6 GHz. Because of their non-pointlike mas-scale structure, these sources are not ideal as astrometric reference objects. Our results demonstrate that VLBI observing programmes conducted primarily with astrometric or geodetic goals can be utilized for astrophysical purposes as well.

[97] arXiv:1807.06833v1 [pdf, vox]

A theoretical tool for the study of radial velocities in the atmospheres of roAp stars

Paola Quitral-Manosalva, Margarida S. Cunha, Oleg Kochukhov
Submitted Wednesday 18 July 2018 @ 09:35:32 GMT
14 pages, 20 figures, Accepted in Monthly Notices of the Royal Astronomical Society

Over the last decade significant amounts of high-spectral and time-resolution spectroscopic data have been acquired for a number of rapidly oscillating Ap stars. Progress in the understanding of the information held by these data requires the development of theoretical models that can be directly compared with them. In this work we present a theoretical model for the radial velocities of roAp stars that takes full account of the coupling between the pulsations and the magnetic field. We explore the impact on the radial velocities of changing the position of the observer, the mode frequency and angular degree, as well as of changing the region of the disk where the elements are concentrated. We find that for integrations over the full disc, in the outermost layers the radial velocity is generally dominated by the acoustic waves, showing a rapid increase in amplitude. The most significant depth-variations in the radial velocity phase are seen for observers directed towards the equator and for even degree modes with frequencies close to, or above the acoustic cutoff. Comparison between the radial velocities obtained for spots of elements located around the magnetic poles and around the magnetic equator, shows that these present distinct amplitude-phase relations, resembling some of the differences seen in the observations. Finally, we discuss the conditions under which one may expect to find false nodes in the pulsation radial velocity of roAp stars.

[98] arXiv:1807.06830v1 [pdf, vox]

Hill-climbing dark inflation

Michal Artymowski, Zygmunt Lalak, Kin-Ya Oda
Submitted Wednesday 18 July 2018 @ 09:31:45 GMT
15 pages, 3 pigures

Within the framework of the scalar-tensor theory we consider a hill-climbing inflation, in which the effective Planck mass increases in time. We obtain the Einstein frame potential with infinitely long and flat plateau as we approach towards the strong coupling regime, together with a run-away vacuum in the GR limit of the theory. The inflation ends with the scalar field rolling down towards infinity, which at the effective level indicates the massless scalar field domination in the Universe. In this scheme we assume that the inflaton is a dark particle, which has no couplings to the Standard Model degrees of freedom (other than the gravitational ones). We discuss the gravitational reheating of the Universe together with its implications on the predictions of the model, including possible amplification of primordial gravitational waves. Our model for the first time realizes explicitly the enhancement of the primordial gravitational waves in the dark inflation scenario.

[99] arXiv:1807.06827v1 [pdf, vox]

Detection opportunity for aromatic signature in Titan s aerosols in the 4.1 to 5.3 micron range

Christophe Mathé, Thomas Gautier, Melissa G. Trainer, Nathalie Carrasco
Submitted Wednesday 18 July 2018 @ 09:21:58 GMT

The Cassini/Huygens mission provided new insights on the chemistry of the upper atmosphere of Titan. The presence of large molecules and ions (>100 s of amu) detected by Cassini at high altitude was not expected, and questions the original assumptions regarding the aerosol formation pathways. From recent laboratory studies, it has been shown that the inclusion of trace amounts of aromatic species drastically impacts the chemistry of aerosol formation and induces observable changes in the properties of the aerosols. In the present work we focus on the effect of one of the simplest nitrogenous aromatics, pyridine (C5H5N), on the infrared signature of Titan s aerosol analogs. We introduce initial gas mixtures of: (i) N2-C5H5N (100%/250ppm), (ii) N2-CH4-C5H5N (99%/1%/250ppm), (iii) N2-CH4 (99%/1%) in a cold plasma discharge. The material produced, herein called tholins, is then analyzed by mid-infrared spectroscopy. When adding pyridine in the discharge, the tholins produced present an aromatic signature in the 4.1-5.3 micron (1850-2450 cm-1) spectral region, attributed to overtones of aromatic C-H out-of-plane bending vibrations. We also observe a spectral shift of the nitrile and iso-nitrile absorption band with the inclusion of pyridine in the gas mixture. These results could help to investigate the data obtained at Titan by the Cassini/VIMS instrument in the 1-5 micron infrared window

[100] arXiv:1807.07435v1 [pdf, vox]

A multimessenger view of galaxies and quasars from now to mid-century

Mauro D'Onofrio, Paola Marziani
Submitted Wednesday 18 July 2018 @ 08:52:01 GMT
43 pages, 8 figures. arXiv admin note: text overlap with arXiv:1801.03298 by other authors

In the next 30 years, a new generation of space and ground-based telescopes will permit to obtain multi-frequency observations of faint sources and, for the first time in human history, to achieve a deep, almost synoptical monitoring of the whole sky. Gravitational wave observatories will detect a Universe of unseen black holes in the merging process over a broad spectrum of mass. Computing facilities will permit new high-resolution simulations with a deeper physical analysis of the main phenomena occurring at different scales. Given these development lines, we first sketch a panorama of the main instrumental developments expected in the next thirty years, dealing not only with electromagnetic radiation, but also from a multi-messenger perspective that includes gravitational waves, neutrinos, and cosmic rays. We then present how the new instrumentation will make it possible to foster advances in our present understanding of galaxies and quasars. We focus on selected scientific themes that are hotly debated today, in some cases advancing conjectures on the solution of major problems that may become solved in the next 30 years.

[101] arXiv:1807.06803v1 [pdf, vox]

Hierarchical search strategy for the efficient detection of gravitational waves from non-precessing coalescing compact binaries with aligned-spins

Bhooshan Gadre, Sanjit Mitra, Sanjeev Dhurandhar
Submitted Wednesday 18 July 2018 @ 07:28:36 GMT
17 pages, 17 figures

In the first two years of Gravitational Wave (GW) Astronomy, half a dozen compact binary coalescences (CBCs) have been detected. As the sensitivities and bandwidths of the detectors improve and new detectors join the network, many more sources are expected to be detected. The goal will not only be to find as many sources as possible in the data but to understand the dynamics of the sources much more precisely. Standard searches are currently restricted to a smaller parameter space which assumes aligned spins. Construction of a larger and denser parameter space, and optimising the resultant increase in false alarms, pose a serious computational challenge. We present here a two-stage hierarchical strategy to search for CBCs in data from a network of detectors and demonstrate the computational advantage in real life scenario by introducing it in the standard {\tt PyCBC} pipeline with the usual restricted parameter space. With this strategy, in simulated data containing stationary Gaussian noise, we obtain a computational gain of $\sim 20$ over the flat search. In real data, we expect the computational gain up to a factor of few. This saving in the computational effort will, in turn, allow us to search for precessing binaries. Freeing up computation time for the regular analyses will provide more options to search for sources of different kinds and to fulfil the never-ending urge for extracting more science out of the data with limited resources.

[102] arXiv:1807.06802v1 [pdf, vox]

CosmicGrowth Simulations CosmicGrowth Simulations---Cosmol​ogical simulations for structure growth studies

Y. P. Jing
Submitted Wednesday 18 July 2018 @ 07:26:42 GMT
Submitted to SCIENCE CHINA Physics, Mechanics & Astronomy

I present a large set of high resolution simulations, called CosmicGrowth Simulations, which were generated with either 8.6 billion or 29 billion particles. As the nominal cosmological model that can match nearly all observations on cosmological scales, I have adopted a flat Cold Dark Matter (CDM) model with a cosmological constant $\Lambda$ (${\Lambda}$CDM). The model parameters have been taken either from the latest result of the WMAP satellite (WMAP ${\Lambda}$CDM) or from the first year's result of the Planck satellite (Planck ${\Lambda}$CDM). Six simulations are produced in the ${\Lambda}$CDM models with two in the Planck model and the others in the WMAP model. In order for studying the nonlinear evolution of the clustering, four simulations were also produced with $8.6$ billion particles for the scale-free models of an initial power spectrum $P(k)\propto k^n$ with $n=0$,$-1$,$-1.5$ or $-2.0$. Furthermore, two radical CDM models (XCDM) are simulated with 8.6 billion particles each. Since the XCDM have some of the model parameters distinct from those of the ${\Lambda}$CDM models, they must be unable to match the observations, but are very useful for studying how the clustering properties depend on the model parameters. The Friends-of-Friends (FoF) halos were identified for each snapshot and subhalos were produced by the Hierarchical Branch Tracing (HBT) algorithm. These simulations form a powerful database to study the growth and evolution of the cosmic structures both in theories and in observations.

[103] arXiv:1807.06798v1 [pdf, vox]

Two blobs in a jet model for the gamma-ray emission in radio galaxies

P. Banasinski, W. Bednarek
Submitted Wednesday 18 July 2018 @ 07:10:27 GMT
14 pages, 7 figures, 1 table, accepted in ApJ

In the unified scheme FR I type radio galaxies are identified with the blazar type active galaxies which jets are aligned at large angles to the line of sight. A few radio galaxies of this type have been discovered to emit GeV-TeV gamma-rays. We consider a scenario which naturally explains the very high energy gamma-ray emission at large angles to the jet axis. It is proposed that two emission regions are present in the jet at this same moment. The inner region (blob I), moves with the large Lorentz factor, producing radiation strongly collimated along the jet axis, as observed in BL Lac type blazars. On the other hand, the outer region (blob II), which moves with the mild Lorentz factor, contains isotropically distributed relativistic electrons in the blob reference frame. These electrons up-scatter mono-directional soft radiation from the blob I preferentially in the direction opposite to the jet motion. Therefore, gamma-rays, produced in the blob II, can be emitted at a relatively large angles to the jet axis in the observer's reference frame. We analyze the basic emission features of such external blob radiation model. The example modeling of the emission from the FR I type radio galaxy, NGC 1275, is presented.

[104] arXiv:1807.06783v1 [pdf, vox]

The Contribution of Dwarf Planets to the Origin of Low Inclination Comets by the Replenishment of Mean Motion Resonances in Debris Disks

Marco A. Muñoz-Gutiérrez, Antonio Peimbert, Bárbara Pichardo
Submitted Wednesday 18 July 2018 @ 05:53:28 GMT
13 pages, 11 figures, Accepted for publication in the AJ

In this work we explore a new dynamical path for the delivery of low-inclination comets. In a configuration formed by an interior giant planet and an exterior massive debris disk, where the mass is accounted for by the 50 largest objects in the disk, the strongest mean motion resonances of the giant, located along the belt, are replenished with new material (test particles) due to the influence of the 50 massive objects. Once in resonance, slow chaotic diffusion stirs the orbital elements of the cometary nuclei enough to encounter the giant and to be scattered by it. When the disk is massive enough, both resonant and non-resonant particles are stirred quickly to encounter the giant and form an scattered disk component, greatly increasing the rate for the delivery of cometary material to the inner part of the system. This mechanism is applicable both to the solar system and extrasolar systems in general. Preliminary results, using a disk as massive as the classical Kuiper belt, indicate that the mechanism here proposed can account for about a tenth of the required injection rate to maintain the population of ecliptic comets in steady state. In a more massive belt of 0.25 M$_\oplus$, an estimated rate of around 0.6 new comets per year is found. Such a high rate would pose a serious risk for the habitability of rocky interior planets, yet would resemble the late heavy bombardment that was present in the early solar system.

[105] arXiv:1807.06758v1 [pdf, vox]

Fast Linearized Coronagraph Optimizer (FALCO) IV. Coronagraph design survey for obstructed and segmented apertures

G. Ruane, A. Riggs, C. T. Coker, S. B. Shaklan, E. Sidick, D. Mawet, J. Jewell, K. Balasubramanian, C. C. Stark
Submitted Wednesday 18 July 2018 @ 03:29:58 GMT
To appear in the Proceedings of the SPIE, vol. 10698

Coronagraph instruments on future space telescopes will enable the direct detection and characterization of Earth-like exoplanets around Sun-like stars for the first time. The quest for the optimal optical coronagraph designs has made rapid progress in recent years thanks to the Segmented Coronagraph Design and Analysis (SCDA) initiative led by the Exoplanet Exploration Program at NASA's Jet Propulsion Laboratory. As a result, several types of high-performance designs have emerged that make use of dual deformable mirrors to (1) correct for optical aberrations and (2) suppress diffracted starlight from obstructions and discontinuities in the telescope pupil. However, the algorithms used to compute the optimal deformable mirror surface tend to be computationally intensive, prohibiting large scale design surveys. Here, we utilize the Fast Linearized Coronagraph Optimizer (FALCO), a tool that allows for rapid optimization of deformable mirror shapes, to explore trade-offs in coronagraph designs for obstructed and segmented space telescopes. We compare designs for representative shaped pupil Lyot and vortex coronagraphs, two of the most promising concepts for the LUVOIR space mission concept. We analyze the optical performance of each design, including their throughput and ability to passively suppress light from partially resolved stars in the presence of low-order aberrations. Our main result is that deformable mirror based apodization can sufficiently suppress diffraction from support struts and inter-segment gaps whose widths are on the order of $\sim$0.1% of the primary mirror diameter to detect Earth-sized planets within a few tens of milliarcseconds from the star.

[106] arXiv:1807.06252v2 [pdf, vox]

An application of the Ghosh & Lamb model to the accretion powered X-ray pulsar X Persei

Fumiaki Yatabe, Kazuo Makishima, Tatehiro Mihara, Motoki Nakajima, Mutsumi Sugizaki, Shunji Kitamoto, Yuki Yoshida, Toshihiro Takagi
Submitted Wednesday 18 July 2018 @ 01:53:50 GMT
11 pages, 9 figures, accepted for publication in PASJ

The accretion-induced pulse-period changes of the Be/X-ray binary pulsar X Persei were investigated over a period of 1996 January to 2017 September. This study utilized the monitoring data acquired with the RXTE/ASM in 1.5$-$12 keV and MAXI/GSC in 2$-$20 keV. The source intensity changed by a factor of 5$-$6 over this period. The pulsar was spinning down for 1996$-$2003, and has been spinning up since 2003, as already reported. The spin up/down rate and the 3$-$12 keV flux, determined every 250 d, showed a clear negative correlation, which can be successfully explained by the accretion torque model proposed by Ghosh & Lamb (1979). When the mass, radius and distance of the neutron star are allowed to vary over a range of 1.0$-$2.4 solar masses, 9.5$-$15 km, and 0.77$-$0.85 kpc, respectively, the magnetic field strength of $B=(4-25) \times10^{13}\ \rm G$ gave the best fits to the observation. In contrast, the observed results cannot be explained by the values of $B\sim10^{12}\ \rm G$ previously suggested for X Persei, as long as the mass, radius, and distance are required to take reasonable values. Assuming a distance of $0.81\pm0.04$ kpc as indicated by optical astrometry, the mass of the neutron star is estimated as $M=2.03\pm0.17$ solar masses.

[107] arXiv:1807.06726v1 [pdf, vox]

A hierarchical Bayesian method for detecting continuous gravitational waves from an ensemble of pulsars

M. Pitkin, C. Messenger, X. Fan
Submitted Wednesday 18 July 2018 @ 01:04:15 GMT
18 pages, 8 figures

When looking for gravitational wave signals from known pulsars, targets have been treated using independent searches. Here we use a hierarchical Bayesian framework to combine observations from individual sources for two purposes: to produce a detection statistic for the whole ensemble of sources within a search, and, to estimate the hyperparameters of the underlying distribution of pulsar ellipticities. Both purposes require us to assume some functional form of the ellipticity distribution, and as a proof of principle we take two toy distributions. One is an exponential distribution,defined by its mean, and the other is a half-Gaussian distribution defined by its width. We show that by incorporating a common parameterized prior ellipticity distribution we can be more efficient at detecting gravitational waves from the whole ensemble of sources than trying to combine observations with a simpler non-hierarchical method. This may allow us to detect gravitational waves from the ensemble before there is confident detection of any single source. We also apply this method using data for 92 pulsars from LIGO's sixth science run. No evidence for a signal was seen, but 90\% upper limits of $3.9\ee{-8}$ and $4.7\ee{-8}$ were set on the mean of an assumed exponential ellipticity distribution and the width of an assumed half-Gaussian ellipticity distribution, respectively.

Submitted Tue, 17 Jul 2018

[108] arXiv:1807.05235v2 [pdf, vox]

The Hawaii Infrared Parallax Program. III. 2MASS J0249-0557 c: A Wide Planetary-mass Companion to a Low-mass Binary in the beta Pic Moving Group

Trent J. Dupuy, Michael C. Liu, Katelyn N. Allers, Beth A. Biller, Kaitlin M. Kratter, Andrew W. Mann, Evgenya L. Shkolnik, Adam L. Kraus, William M. J. Best
Submitted Tuesday 17 July 2018 @ 22:19:14 GMT
Accepted to AJ, only change is color scheme of figures

We have discovered a wide planetary-mass companion to the $\beta$ Pic moving group member 2MASSJ02495639-05573​52 (M6 VL-G) using CFHT/WIRCam astrometry from the Hawaii Infrared Parallax Program. In addition, Keck laser guide star adaptive optics aperture-masking interferometry shows that the host is itself a tight binary. Altogether, 2MASSJ0249-0557ABc is a bound triple system with an $11.6^{+1.0}_{-1.3}$ $M_{\rm Jup}$ object separated by $1950\pm200$ AU (40") from a relatively close ($2.17\pm0.22$ AU, 0.04") pair of $48^{+12}_{-13}$ $M_{\rm Jup}$ and $44^{+11}_{-14}$ $M_{\rm Jup}$ objects. 2MASSJ0249-0557AB is one of the few ultracool binaries to be discovered in a young moving group and the first confirmed in the $\beta$ Pic moving group ($22\pm6$ Myr). The mass, absolute magnitudes, and spectral type of 2MASSJ0249-0557 c (L2 VL-G) are remarkably similar to those of the planet $\beta$ Pic b (L2, $13.0^{+0.4}_{-0.3}$ $M_{\rm Jup}$). We also find that the free-floating object 2MASSJ2208+2921 (L3 VL-G) is another possible $\beta$ Pic moving group member with colors and absolute magnitudes similar to $\beta$ Pic b and 2MASSJ0249-0557 c. $\beta$ Pic b is the first directly imaged planet to have a "twin," namely an object of comparable properties in the same stellar association. Such directly imaged objects provide a unique opportunity to measure atmospheric composition, variability, and rotation across different pathways of assembling planetary-mass objects from the same natal material.

[109] arXiv:1807.06687v1 [pdf, vox]

Accelerated evolution of convective simulations

Evan H. Anders, Benjamin P. Brown, Jeffrey S. Oishi
Submitted Tuesday 17 July 2018 @ 22:02:23 GMT
Submitted to PRFluids. 14 pages, 6 figures, 2 tables, 2 appendices

High Peclet number, turbulent convection is a classic system with a large timescale separation between flow speeds and equilibration time. In this paper, we present a method of achieving Accelerated Evolution (AE) of convective simulations which fast-forwards through the long thermal evolution of these systems, and we test the validity of this method. The AE procedure involves measuring the dynamics of convection early in a simulation and using its characteristics to adjust the mean thermodynamic profile within the domain towards its evolved state. We study Rayleigh-B\'enard convection as a test case for AE. Evolved flow properties of AE solutions are measured to be within a few percent of solutions which are reached through Standard Evolution (SE) over a full thermal timescale. At the highest values of the Rayleigh number at which we compare SE and AE, we find that AE solutions require roughly an order of magnitude fewer cpu-hours to compute than SE solutions.

[110] arXiv:1807.06681v1 [pdf, vox]

Chemical Compositions of Field and Globular Cluster RR Lyrae Stars: I. NGC 3201

D. Magurno, C. Sneden, V. F. Braga, G. Bono, M. Mateo, S. E. Persson, M. Dall'Ora, M. Marengo, M. Monelli, J. R. Neeley
Submitted Tuesday 17 July 2018 @ 21:35:53 GMT

We present a detailed spectroscopic analysis of horizontal branch stars in the globular cluster NGC 3201. We collected optical (4580-5330 A), high resolution (~34,000), high signal-to-noise ratio (~200) spectra for eleven RR Lyrae stars and one red horizontal branch star with the multifiber spectrograph M2FS at the 6.5m Magellan telescope at the Las Campanas Observatory. From measured equivalent widths we derived atmospheric parameters and abundance ratios for {\alpha} (Mg, Ca, Ti), iron peak (Sc, Cr, Ni, Zn) and s-process (Y) elements. We found that NGC 3201 is a homogeneous, mono-metallic ([Fe/H]=-1.47 +- 0.04), {\alpha}-enhanced ([{\alpha}/Fe]=0.37 +- 0.04) cluster. The relative abundances of the iron peak and s-process elements were found to be consistent with solar values. In comparison with other large stellar samples, NGC 3201 RR Lyraes have similar chemical enrichment histories as do those of other old (t>10 Gyr) Halo components (globular clusters, red giants, blue and red horizontal branch stars, RR Lyraes). We also provided a new average radial velocity estimate for NGC 3201 by using a template velocity curve to overcome the limit of single epoch measurements of variable stars: Vrad=494 +- 2 km s-1({\sigma}=8 km s-1).

[111] arXiv:1807.06680v1 [pdf, vox]

Protostellar Outflows at the EarliesT Stages (POETS). I. Radio thermal jets at high resolution nearby H$_2$O maser sources

A. Sanna, L. Moscadelli, C. Goddi, V. Krishnan, F. Massi
Submitted Tuesday 17 July 2018 @ 21:31:02 GMT
25 pages, 7 figures, 4 tables, accepted by Astronomy & Astrophysics

Abridged. Methods. We made use of the Karl G. Jansky Very Large Array (VLA) in the B configuration at K band, and in the A configuration at both Ku and C bands, in order to image the radio continuum emission towards 25 H$_2$O maser sites with an angular resolution and thermal rms of the order of $0.1''$ and 10 $\mu$Jy beam$^{-1}$, respectively. These targets add to our pilot study of 11 maser sites presented in Moscadelli et al. (2016). The sample of H$_2$O maser sites was selected among those regions having an accurate distance measurement, obtained through maser trigonometric parallaxes, and H$_2$O maser luminosities in excess of 10$^{-6}$ L$_{\odot}$. Results. We present high-resolution radio continuum images of 33 sources belonging to 25 star-forming regions. In each region, we detect radio continuum emission within a few 1000 au of the H$_2$O masers' position; 50% of the radio continuum sources are associated with bolometric luminosities exceeding 5 $\times$ 10$^{3}$ L$_{\odot}$, including W33A and G240.32$+$0.07. We provide a detailed spectral index analysis for each radio continuum source, based on the integrated fluxes at each frequency, and produce spectral index maps with the multi-frequency-synt​hesis deconvolution algorithm of CASA. The radio continuum emission traces thermal bremsstrahlung in (proto)stellar winds and jets, with flux densities at 22 GHz below 3 mJy, and spectral index values between $-0.1$ and 1.3. We prove a strong correlation ($r>$0.8) between the radio continuum luminosity (L$_{\rm rad}$) and the H$_2$O maser luminosity (L$_{\rm H_2O}$) of ($\rm L_{8GHz}/mJy\times kpc^2)=10^{3.8}\time​s(L_{H_2O}/L_{\odot}​)^{0.74}$. Since H$_2$O masers are excited through shocks driven by (proto)stellar winds and jets, these results provide support to the idea that the radio continuum emission around young stars is dominated by shock-ionization.

[112] arXiv:1807.06678v1 [pdf, vox]

The optical design of the six-meter CCAT-prime and Simons Observatory telescopes

Stephen C. Parshley, Michael D. Niemack, Richard Hills, Simon R. Dicker, Rolando Dünner, Jens Erler, Patricio A. Gallardo, Jon E. Gudmundsson, Terry Herter, Brian J. Koopman, Michele Limon, Frederick T. Matsuda, Philip Mauskopf, Dominik A. Riechers, Gordon J. Stacey, Eve M. Vavagiakis
Submitted Tuesday 17 July 2018 @ 21:23:05 GMT
Event: SPIE Astronomical Telescopes + Instrumentation, 2018, Austin, Texas, USA; Proceedings Volume 10700, Ground-based and Airborne Telescopes VII; 1070041 (2018)

A common optical design for a coma-corrected, 6-meter aperture, crossed-Dragone telescope has been adopted for the CCAT-prime telescope of CCAT Observatory, Inc., and for the Large Aperture Telescope of the Simons Observatory. Both are to be built in the high altitude Atacama Desert in Chile for submillimeter and millimeter wavelength observations, respectively. The design delivers a high throughput, relatively flat focal plane, with a field of view 7.8 degrees in diameter for 3 mm wavelengths, and the ability to illuminate >100k diffraction-limited beams for < 1 mm wavelengths. The optics consist of offset reflecting primary and secondary surfaces arranged in such a way as to satisfy the Mizuguchi-Dragone criterion, suppressing first-order astigmatism and maintaining high polarization purity. The surface shapes are perturbed from their standard conic forms in order to correct coma aberrations. We discuss the optical design, performance, and tolerancing sensitivity. More information about CCAT-prime can be found at ccatobservatory.org and about Simons Observatory at simonsobservatory.or​g.

[113] arXiv:1807.06675v1 [pdf, vox]

CCAT-prime: a novel telescope for submillimeter astronomy

Stephen C. Parshley, Jörg Kronshage, James Blair, Terry Herter, Mike Nolta, Gordon J. Stacey, Andrew Bazarko, Frank Bertoldi, Ricardo Bustos, Donald B. Campbell, Scott Chapman, Nicholas Cothard, Mark Devlin, Jens Erler, Michel Fich, Patricio A. Gallardo, Riccardo Giovanelli, Urs Graf, Scott Gramke, Martha P. Haynes, Richard Hills, Michele Limon, Jeffrey G. Mangum, Jeff McMahon, Michael D. Niemack, Thomas Nikola, Markus Omlor, Dominik A. Riechers, Karl Steeger, Jürgen Stutzki, Eve M. Vavagiakis
Submitted Tuesday 17 July 2018 @ 21:14:15 GMT
Event: SPIE Astronomical Telescope + Instrumentation, 2018, Austin, Texas, USA; Proceedings Volume 10700, Ground-based and Airborne Telescopes VII; 107005X (2018)

The CCAT-prime telescope is a 6-meter aperture, crossed-Dragone telescope, designed for millimeter and sub-millimeter wavelength observations. It will be located at an altitude of 5600 meters, just below the summit of Cerro Chajnantor in the high Atacama region of Chile. The telescope's unobscured optics deliver a field of view of almost 8 degrees over a large, flat focal plane, enabling it to accommodate current and future instrumentation fielding >100k diffraction-limited beams for wavelengths less than a millimeter. The mount is a novel design with the aluminum-tiled mirrors nested inside the telescope structure. The elevation housing has an integrated shutter that can enclose the mirrors, protecting them from inclement weather. The telescope is designed to co-host multiple instruments over its nominal 15 year lifetime. It will be operated remotely, requiring minimum maintenance and on-site activities due to the harsh working conditions on the mountain. The design utilizes nickel-iron alloy (Invar) and carbon-fiber-reinfor​ced polymer (CFRP) materials in the mirror support structure, achieving a relatively temperature-insensit​ive mount. We discuss requirements, specifications, critical design elements, and the expected performance of the CCAT-prime telescope. The telescope is being built by CCAT Observatory, Inc., a corporation formed by an international partnership of universities. More information about CCAT and the CCAT-prime telescope can be found at www.ccatobservatory.​org.

[114] arXiv:1807.06673v1 [pdf, vox]

The Frequency of Dwarf Galaxy Multiples at Low Redshift in SDSS vs. Cosmological Expectations

Gurtina Besla, David R. Patton, Sabrina Stierwalt, Vicente Rodriguez-Gomez, Ekta Patel, Nitya J. Kallivayalil, Kelsey Johnson, Sarah Pearson, George Privon, Mary E. Putman
Submitted Tuesday 17 July 2018 @ 21:08:33 GMT
21 pages, 16 Figures, submitted to MNRAS (Referee stage ; Comments are welcome)

We quantify the frequency of companions of low redshift ($0.013 < z < 0.0252$), dwarf galaxies ($2 \times 10^8$ M$_\odot <$ M$_{*} < 5 \times 10^9$ M$_\odot$) that are isolated from more massive galaxies in SDSS and compare against cosmological expectations using mock observations of the Illustris simulation. Dwarf multiples are defined as 2 or more dwarfs that have angular separations > 55'', projected separations r$_p < 150$ kpc and relative line-of-sight velocities $\Delta V_{\rm LOS} < 150$ km/s. While the mock catalogs predict a factor of 2 more isolated dwarfs than observed in SDSS, the mean number of observed companions per dwarf is $N_c \sim 0.04$, in good agreement with Illustris when accounting for SDSS sensitivity limits. Removing these limits in the mock catalogs predicts $N_c\sim 0.06$ for future surveys (LSST, DESI), which will be complete to M$_* = 2\times 10^8$ M$_\odot$. The 3D separations of mock dwarf multiples reveal a contamination fraction of $\sim$40% in observations from projection effects. Most isolated multiples are pairs; triples are rare and it is cosmologically improbable that bound groups of dwarfs with more than 3 members exist within the parameter range probed in this study. We find that $<$1% of LMC-analogs in the field have an SMC-analog companion. The fraction of dwarf "Major Pairs'' (stellar mass ratio $>$1:4) steadily increases with decreasing Primary stellar mass, whereas the cosmological "Major Merger rate'' (per Gyr) has the opposite behaviour. We conclude that cosmological simulations can be reliably used to constrain the fraction of dwarf mergers across cosmic time.

[115] arXiv:1807.06670v1 [pdf, vox]

Extragalactic Proper Motions: Gravitational Waves and Cosmology

Jeremy Darling, Alexandra Truebenbach, Jennie Paine
Submitted Tuesday 17 July 2018 @ 20:54:53 GMT
An ngVLA Science Book chapter. 8 pages, 1 figure

Extragalactic proper motions can reveal a variety of cosmological and local phenomena over a range of angular scales. These include observer-induced proper motions, such as the secular aberration drift caused by the solar acceleration about the Galactic Center and a secular extragalactic parallax resulting from our motion with respect to the cosmic microwave background rest frame. Cosmological effects include anisotropic expansion, transverse peculiar velocities induced by large scale structure, and the real-time evolution of the baryon acoustic oscillation. Long-period gravitational waves can deflect light rays, producing an apparent quadrupolar proper motion signal. We review these effects, their imprints on global correlated extragalactic proper motions, their expected amplitudes, the current best measurements (if any), and predictions for Gaia. Finally, we describe a possible long-baseline ngVLA program to measure or constrain these proper motion signals. In most cases, the ngVLA can surpass or complement the expected end-of-mission performance of the Gaia mission.

[116] arXiv:1807.06662v1 [pdf, vox]

Actinide Production in Neutron-Rich Ejecta of a Neutron Star Merger

Erika M. Holmbeck, Rebecca Surman, Trevor M. Sprouse, Matthew R. Mumpower, Nicole Vassh, Timothy C. Beers, Toshihiko Kawano
Submitted Tuesday 17 July 2018 @ 20:36:21 GMT
14 pages, 19 figures

The rapid-neutron-captur​e ("r") process is responsible for synthesizing many of the heavy elements observed in both the solar system and Galactic metal-poor halo stars. Simulations of r-process nucleosynthesis can reproduce abundances derived from observations with varying success, but so far fail to account for the observed over-enhancement of actinides, present in about 30% of r-process-enhanced stars. In this work, we investigate actinide production in the dynamical ejecta of a neutron star merger and explore if varying levels of neutron richness can reproduce the actinide boost. We also investigate the sensitivity of actinide production on nuclear physics properties: fission distribution, beta-decay, and mass model. For most cases, the actinides are over-produced in our models if the initial conditions are sufficiently neutron-rich for fission cycling. We find that actinide production can be so robust in the dynamical ejecta that an additional lanthanide-rich, actinide-poor component is necessary in order to match observations of actinide-boost stars. We present a simple actinide-dilution model that folds in estimated contributions from two nucleosynthetic sites within a merger event. Our study suggests that while the dynamical ejecta of a neutron star merger is a likely production site for the formation of actinides, a significant contribution from another site or sites (e.g., the neutron star merger accretion disk wind) is required to explain abundances of r-process-enhanced, metal-poor stars.

[117] arXiv:1807.06658v1 [pdf, vox]

All Transverse Motion is Peculiar: Connecting the Proper Motions of Galaxies to the Matter Power Spectrum

Jeremy Darling, Alexandra E. Truebenbach
Submitted Tuesday 17 July 2018 @ 20:24:48 GMT
Accepted for publication by ApJ. 14 pages, 10 figures

In an isotropic and homogeneous Hubble expansion, all transverse motion is peculiar. Like the radial peculiar velocities of galaxies, transverse peculiar velocities are a means to trace the density of matter that does not rely on light tracing mass. Unlike radial peculiar velocity measurements that require precise redshift-independent distances in order to distinguish between the Hubble expansion and the observed redshift, transverse peculiar velocities can be measured using redshifts alone as a proxy for distance. Extragalactic proper motions can therefore directly measure peculiar velocities and probe the matter power spectrum. Here we develop two-point transverse velocity correlation statistics and demonstrate their dependence on the matter power spectrum. We predict the power in these correlation statistics as a function of the physical separation, angular separation, and distance of pairs of galaxies and demonstrate that the effect of large scale structure on transverse motions is best measured for pairs of objects with comoving separations less than about 50 Mpc. Transverse peculiar velocities induced by large scale structure should be observable as proper motions using long baseline radio interferometry or space-based optical astrometry.

[118] arXiv:1807.06647v1 [pdf, vox]

Dynamical Evolution of the Early Solar System

David Nesvorny
Submitted Tuesday 17 July 2018 @ 20:12:03 GMT
Posted with permission from the Annual Review of Astronomy and Astrophysics, Volume 56 \copyright\ by Annual Reviews, http://www.annualrev​iews.org. This is a preprint version of the article has not been reviewed, edited, or prepared for publication by Annual Reviews. See http://www.annualrev​iews.org for the published version

Several properties of the Solar System, including the wide radial spacing of the giant planets, can be explained if planets radially migrated by exchanging orbital energy and momentum with outer disk planetesimals. Neptune's planetesimal-driven migration, in particular, has a strong advocate in the dynamical structure of the Kuiper belt. A dynamical instability is thought to have occurred during the early stages with Jupiter having close encounters with a Neptune-class planet. As a result of the encounters, Jupiter acquired its current orbital eccentricity and jumped inward by a fraction of an au, as required for the survival of the terrestrial planets and from asteroid belt constraints. Planetary encounters also contributed to capture of Jupiter Trojans and irregular satellites of the giant planets. Here we discuss the dynamical evolution of the early Solar System with an eye to determining how models of planetary migration/instabilit​y can be constrained from its present architecture.

[119] arXiv:1807.07424v1 [pdf, vox]

Propagation of Electromagnetic Waves in MOG: Gravitational Lensing

Sohrab Rahvar, J. W. Moffat
Submitted Tuesday 17 July 2018 @ 19:43:25 GMT
7 pages

We investigate the solution of Maxwell's equations in curved spacetime within the framework of Modified Gravity (MOG). We show that besides the null-geodesic treatment of photons in MOG, using Maxwell's equations and coupling the Poynting vector with the extra vector sector of gravitation in MOG, we can extract the equation for the propagation of light. We obtain Fermat's potential and calculate the deflection angle of light during lensing from a point-like star. Our results show that the deflection angle obtained from the solution of the wave equation in MOG is identical to the null-geodesic solution.

[120] arXiv:1807.06628v1 [pdf, vox]

The High Mass Slope of the IMF

Antonio Parravano, David Hollenbach, Christopher F. McKee
Submitted Tuesday 17 July 2018 @ 19:13:56 GMT
19 pages, 10 figures

Recent papers have found that the inferred slope of the high-mass ($>1.5$ M$_\odot$) IMF for field stars in the solar vicinity has a larger value ($\sim 1.7-2.1$) than the slopes ($\sim 1.2-1.7$; Salpeter= 1.35) inferred from numerous studies of young clusters. We attempt to reconcile this apparent contradiction. Stars mostly form in Giant Molecular Clouds, and the more massive stars ($\gtrsim 3$ M$_\odot$) may have insufficient time before their deaths to uniformly populate the solar circle of the Galaxy. We examine the effect of small sample volumes on the {\it apparent} slope, $\Gamma_{\rm app}$, of the high-mass IMF by modeling the present day mass function (PDMF) over the mass range $1.5-6$ M$_\odot$. Depending on the location of the observer along the solar circle and the size of the sample volume, the apparent slope of the IMF can show a wide variance, with typical values steeper than the underlying universal value $\Gamma$. We show, for example, that the PDMFs observed in a small (radius $\sim 200$ pc) volume randomly placed at the solar circle have a $\sim 15-30$\% likelihood of resulting in $\Gamma_{\rm app} \gtrsim \Gamma+ 0.35$ because of inhomogeneities in the surface densities of more massive stars. If we add the a priori knowledge that the Sun currently lies in an interarm region, where the star formation rate is lower than the average at the solar circle, we find an even higher likelihood ($\sim 50-60\%$ ) of $\Gamma_{\rm app} \gtrsim \Gamma+0.35$, corresponding to $\Gamma_{\rm app} \gtrsim 1.7$ when the underlying $\Gamma= 1.35$.

[121] arXiv:1807.07421v1 [pdf, vox]

Observational constraints on the tilted spatially-flat and the untilted nonflat $φ$CDM dynamical dark energy inflation models

Chan-Gyung Park, Bharat Ratra
Submitted Tuesday 17 July 2018 @ 18:36:35 GMT
21 pages, 14 figures, 5 tables. arXiv admin note: substantial text overlap with arXiv:1803.05522, arXiv:1801.00213

We constrain tilted spatially-flat and untilted nonflat scalar field ($\phi$) dynamical dark energy inflation ($\phi$CDM) models by using Planck 2015 cosmic microwave background (CMB) anisotropy measurements and recent baryonic acoustic oscillation distances data, Type Ia supernovae apparent magnitude observations, Hubble parameter measurements, and growth rate data. We assume an inverse power-law scalar field potential energy density $V(\phi)=V_0 \phi^{-\alpha}$. We find that the combination of the CMB data with the four non-CMB data sets significantly improves parameter constraints, including strengthening the evidence for nonflatness in the untilted nonflat $\phi$CDM model from $1.8\sigma$ for the CMB data alone to more than $3.1\sigma$ for the combined data. In the untilted nonflat $\phi$CDM model current observations favor a spatially closed universe in which spatial curvature contributes about two-thirds of a percent of the current cosmological energy budget. The tilted flat $\phi$CDM model is a 0.4$\sigma$ better fit to the data than is the standard tilted flat $\Lambda$CDM model: current data is unable to rule out dynamical dark energy. The tilted nonflat $\phi$CDM model is more consistent with the Dark Energy Survey constraints on the current value of the rms amplitude of mass fluctuations ($\sigma_8$) as a function of the current value of the nonrelativistic matter density parameter ($\Omega_m$) but does not provide as good a fit to the smaller-angle CMB anisotropy data as does the standard tilted flat $\Lambda$CDM model. Some measured cosmological parameter values differ significantly when determined using the tilted flat and the untilted nonflat $\phi$CDM models, including the cold dark matter density parameter and the reionization optical depth.

[122] arXiv:1807.06616v1 [pdf, vox]

A New Generation of Cool White Dwarf Atmosphere Models. I. Theoretical Framework and Applications to DZ Stars

Simon Blouin, Patrick Dufour, Nicole F. Allard
Submitted Tuesday 17 July 2018 @ 18:32:54 GMT
18 pages, 19 figures. Accepted for publication in The Astrophysical Journal

The photospheres of the coolest helium-atmosphere white dwarfs are characterized by fluid-like densities. Under those conditions, standard approximations used in model atmosphere codes are no longer appropriate. Unfortunately, the majority of cool He-rich white dwarfs show no spectral features, giving us no opportunities to put more elaborate models to the test. In the few cases where spectral features are observed (such as in cool DQ or DZ stars), current models completely fail to reproduce the spectroscopic data, signaling shortcomings in our theoretical framework. In order to fully trust parameters derived solely from the energy distribution, it is thus important to at least succeed in reproducing the spectra of the few coolest stars exhibiting spectral features, especially since such stars possess even less extreme physical conditions due to the presence of heavy elements. In this paper, we revise every building block of our model atmosphere code in order to eliminate low-density approximations. Our updated white dwarf atmosphere code incorporates state-of-the-art constitutive physics suitable for the conditions found in cool helium-rich stars (DC and DZ white dwarfs). This includes new high-density metal line profiles, nonideal continuum opacities, an accurate equation of state and a detailed description of the ionization equilibrium. In particular, we present new ab initio calculations to assess the ionization equilibrium of heavy elements (C, Ca, Fe, Mg and Na) in a dense helium medium and show how our improved models allow us to achieve better spectral fits for two cool DZ stars, Ross 640 and LP 658-2.

[123] arXiv:1807.06603v1 [pdf, vox]

Numerical simulations of supernova remnants in turbulent molecular clouds

Dong Zhang, Roger A. Chevalier
Submitted Tuesday 17 July 2018 @ 18:00:08 GMT
17 pages, 10 figures, 1 table, submitted

Core-collapse supernova (SN) explosions may occur in the highly inhomogeneous molecular clouds (MCs) in which their progenitors were born. We perform a series of 3-dimensional hydrodynamic simulations to model the interaction between an individual supernova remnant (SNR) and a turbulent MC medium, in order to investigate possible observational evidence for the turbulent structure of MCs. We find that the properties of SNRs are mainly controlled by the mean density of the surrounding medium, while a SNR in a more turbulent medium with higher supersonic turbulent Mach number shows lower interior temperature, lower radial momentum, and dimmer X-ray emission compared to one in a less turbulent medium with the same mean density. We compare our simulations to observed SNRs, in particular, to W44, W28 and IC 443. We estimate that the mean density of the ambient medium is $\sim 10\,$cm$^{-3}$ for W44 and W28. The MC in front of IC 443 has a density of $\sim 100\,$cm$^{-3}$. We also predict that the ambient MC of W44 is more turbulent than that of W28 and IC 443. The ambient medium of W44 and W28 has significantly lower average density than that of the host giant MC. This result may be related to the stellar feedback from the SNRs' progenitors. Alternatively, SNe may occur close to the interface between molecular gas and lower density atomic gas. The region of shocked MC is then relatively small and the breakout into the low density atomic gas comprises most of the SNR volume.

[124] arXiv:1807.06598v1 [pdf, vox]

Ring Galaxies Through Off-Center Minor Collisions by Tuning Bulge-to-Disk Mass Ratio of Progenitors

Guangwen Chen, Xufen Wu, Xu Kong, Wen-Juan Liu, HongSheng Zhao
Submitted Tuesday 17 July 2018 @ 18:00:02 GMT
21 pages, 17 figures, accepted for publication in ApJ

Collisional ring galaxies (CRGs) are formed through off-center collisions between a target galaxy and an intruder dwarf galaxy. We study the mass distribution and kinematics of the CRGs by tuning the bulge-to-disk mass ratio ($B/D$) for the progenitor, i.e., the target galaxy. We find that the lifetime of the ring correlates with the initial impact velocity vertical to the disk plane (i.e., $v_{\rm z0}$). Three orbits for the collisional galaxy pair, on which clear and asymmetric rings form after collisions, are selected to perform the N-body simulations at different values of $B/D$ for the progenitor. It is found that, the ring structures are the strongest for the CRGs with small values of $B/D$. The S\'{e}rsic index, $n$, of the central remnant in the target galaxy becomes larger after collision. Moreover, the S\'{e}rsic index of a central remnant strongly correlates with the initial value of $B/D$ for the progenitor. A bulge-less progenitor results in a late-type object in the center of the ring galaxy, whereas a bulge-dominated progenitor leads to an early-type central remnant. Progenitors with $B/D\in [0.1,~0.3]$, i.e., minor bulges, leave central remnants with $n\approx 4$. These results provide a possible explanation for the formation of a recently observed CRG with an early-type central nucleus, SDSS J1634+2049. In addition, we find that the radial and azimuthal velocity profiles for a ring galaxy are more sensitive to the $B/D$ than the initial relative velocity of the progenitor.

[125] arXiv:1807.06599v1 [pdf, vox]

From Manifolds to Lagrangian Coherent Structures in galactic bar models

Patricia Sanchez-Martin, Josep. J. Masdemont, Merce Romero-Gomez
Submitted Tuesday 17 July 2018 @ 18:00:02 GMT
Accepted for publication in A&A, 15 pages, 21 figures

We study the dynamics near the unstable Lagrangian points in galactic bar models using dynamical system tools in order to determine the global morphology of a barred galaxy. We aim at the case of non-autonomous models, in particular with secular evolution, by allowing the bar pattern speed to decrease with time. We extend the concept of manifolds widely used in the autonomous problem to the Lagrangian Coherent Structures (LCS), widely used in fluid dynamics, which behave similar to the invariant manifolds driving the motion. After adapting the LCS computation code to the galactic dynamics problem, we apply it to both the autonomous and non-autonomous problems, relating the results with the manifolds and identifying the objects that best describe the motion in the non-autonomous case. We see that the strainlines coincide with the first intersection of the stable manifold when applied to the autonomous case, while, when the secular model is used, the strainlines still show the regions of maximal repulsion associated to both the corresponding stable manifolds and regions with a steep change of energy. The global morphology of the galaxy predicted by the autonomous problem remains unchanged.

[126] arXiv:1807.06595v1 [pdf, vox]

Evidence for Cosmic-Ray Escape in the Small Magellanic Cloud using Fermi Gamma-rays

Laura A. Lopez, Katie Auchettl, Tim Linden, Alberto D. Bolatto, Todd A. Thompson, Enrico Ramirez-Ruiz
Submitted Tuesday 17 July 2018 @ 18:00:01 GMT
12 pages, 8 figures, submitted to ApJ

Galaxy formation simulations demonstrate that cosmic-ray (CR) feedback may be important in the launching of galactic-scale winds. CR protons dominate the bulk of the CR population, yet most observational constraints of CR feedback come from synchrotron emission of CR electrons. In this paper, we present an analysis of 105 months of Fermi Gamma-ray Space Telescope observations of the Small Magellanic Cloud (SMC), with the aim of exploring CR feedback and transport in an external galaxy. We produce maps of the 2-300 GeV emission and detect statistically significant, extended emission along the Bar and the Wing, where active star formation is occurring. Gamma-ray emission is not detected above 13 GeV, and we set stringent upper-limits on the flux above this energy. We find the best fit to the gamma-ray spectrum is a single-component model with a power-law of index $\Gamma=-2.11\pm0.06​\pm0.06$ and an exponential cutoff energy of $E_{\rm c} =13.1\pm5.1\pm1.6$ GeV. We assess the relative contribution of pulsars and CRs to the emission, and we find that pulsars may produce up to 14$^{+4}_{-2}$% of the flux above 100 MeV. Thus, we attribute most of the gamma-ray emission (based on its spectrum and morphology) to CR interactions with the ISM. We show that the gamma-ray emissivity of the SMC is five times smaller than that of the Milky Way and that the SMC is far below the calorimetric limit, where all CR protons experience pion losses. We interpret these findings as evidence that CRs are escaping the SMC via advection and diffusion.

[127] arXiv:1807.06597v1 [pdf, vox]

First Core Properties: From Low- to High-mass Star Formation

Asmita Bhandare, Rolf Kuiper, Thomas Henning, Christian Fendt, Gabriel-Dominique Marleau, Anders Kölligan
Submitted Tuesday 17 July 2018 @ 18:00:01 GMT
Accepted for publication in A&A. 20 pages, 11 figures and 3 tables

In this study, the main goal is to understand the molecular cloud core collapse through the stages of first and second hydrostatic core formation. We investigate the properties of Larson's first and second cores following the evolution of the molecular cloud core until formation of Larson's cores. We expand these collapse studies for the first time to span a wide range of initial cloud masses from 0.5 to 100 Msun. Understanding the complexity of the numerous physical processes involved in the very early stages of star formation requires detailed thermodynamical modeling in terms of radiation transport and phase transitions. For this we use a realistic gas equation of state via a density and temperature-dependen​t adiabatic index and mean molecular weight to model the phase transitions. We use a gray treatment of radiative transfer coupled with hydrodynamics to simulate Larson's collapse in spherical symmetry. We reveal a dependence of a variety of first core properties on the initial cloud mass. The first core radius and mass increase from the low-mass to the intermediate-mass regime and decrease from the intermediate-mass to the high-mass regime. The lifetime of first cores strongly decreases towards the intermediate- and high-mass regime. Our studies show the presence of a transition region in the intermediate-mass regime. Low-mass protostars tend to evolve through two distinct stages of formation which are related to the first and second hydrostatic cores. In contrast, in the high-mass star formation regime, the collapsing cloud cores rapidly evolve through the first collapse phase and essentially immediately form Larson's second cores.

[128] arXiv:1807.06584v1 [pdf, vox]

Discovery of two bright DO-type white dwarfs

Nicole Reindl, Stephan Geier, Roy H. Østensen
Submitted Tuesday 17 July 2018 @ 17:56:46 GMT
7 pages, 4 figures, accepted for publication in MNRAS

We discovered two bright DO-type white dwarfs, GALEXJ053628.3+54485​4 (J0536+5448) and GALEX231128.0+292935​(J2311+2929), which rank among the eight brightest DO-type white dwarfs known. Our non-LTE model atmosphere analysis reveals effective temperatures and surface gravities of $T_{\mathrm{eff}}=80​000\pm4600\,\mathrm{​K}$ and $\log \mathrm{g}=8.25\pm0.​15$ for J0536+5448 and $T_{\mathrm{eff}}=69​400\pm900\,\mathrm{K​}$ and $\log \mathrm{g}=7.80\pm0.​06$ for J2311+2929. The latter shows a significant amount of carbon in its atmosphere ($C=0.003^{+0.005}_{​-0.002}$, by mass), while for J0536+5448 we could derive only an upper limit of $C<0.003$. Furthermore, we calculated spectroscopic distances for the two stars and found a good agreement with the distances derived from the Gaia parallaxes.

[129] arXiv:1807.06579v1 [pdf, vox]

Primordial Gravitational Waves and the Swampland

Mafalda Dias, Jonathan Frazer, Ander Retolaza, Alexander Westphal
Submitted Tuesday 17 July 2018 @ 17:45:50 GMT
revtex, 4 pages, 2 figures

The swampland conjectures seek to distinguish effective field theories which can be consistently embedded in a theory of quantum gravity from those which can not (and are hence referred to as being in the swampland). We consider two such conjectures, known as the Swampland Distance and de Sitter Conjectures, showing that taken together they place bounds on the amplitude of primordial gravitational waves generated during single field slow-roll inflation. The bounds depend on two parameters which for reasonable estimates restrict the tensor-to-scalar ratio to be within reach of future surveys.

[130] arXiv:1807.06569v1 [pdf, vox]

In-medium enhancement of the modified Urca neutrino reaction rates

P. S. Shternin, M. Baldo, P. Haensel
Submitted Tuesday 17 July 2018 @ 17:23:00 GMT
8 pages, 3 figures

We calculate modified Urca neutrino emission rates in the dense nuclear matter in neutron star cores. We find that these rates are strongly enhanced in the beta-stable matter in regions of the core close to the direct Urca process threshold. This enhancement can be tracked to the use of the in-medium nucleon spectrum in the virtual nucleon propagator. We describe the in-medium nucleon scattering in the non-relativistic Bruckner-Hartree-Foc​k framework taking into account two-body as well as the effective three-body forces, although the proposed enhancement does not rely on a particular way of the nucleon interaction treatment. Finally we suggest a simple approximate expression for the emissivity of the n-branch of the modified Urca process that can be used in the neutron stars cooling simulations with any nucleon equation of state of dense matter.

[131] arXiv:1807.06567v1 [pdf, vox]

RadFil: a Python Package for Building and Fitting Radial Profiles for Interstellar Filaments

Catherine Zucker, Hope How-Huan Chen
Submitted Tuesday 17 July 2018 @ 17:20:11 GMT
Accepted for publication in The Astrophysical Journal

We present RadFil, a publicly available Python package that gives users full control over how to build and fit radial density profiles for interstellar filaments. RadFil builds filament profiles by taking radial cuts across the spine of a filament, thereby preserving the radial structure of the filament across its entire length. Pre-existing spines can be inputted directly into RadFil, or can be computed using the FilFinder package as part of the RadFil workflow. We provide Gaussian and Plummer built-in fitting functions, in addition to a background subtraction estimator, which can be fit to the entire ensemble of radial cuts or an average radial profile for the filament. Users can tweak parameters like the radial cut sampling interval, the background subtraction estimation radii, and the Gaussian/Plummer fitting radii. As a result, RadFil can provide treatment of how the resulting filament properties rely on systematics in the building and fitting process. We walk through the typical RadFil workflow and compare our results to those from an independent radial density profile code obtained using the same data; we find that our results are entirely consistent. RadFil is open source and available on GitHub. We also provide a complete working tutorial of the code available as a Jupyter notebook which users can download and run themselves.

[132] arXiv:1807.06562v1 [pdf, vox]

A new photolithography based technique to mass produce microlens+fibre based integralfield units (IFUs) for 2D spectroscopy

Sabyasachi Chattopadhyay, Vishal Joshi, A. N. Ramaprakash, Deepa Modi, Abhay Kohak, Haeun Chung
Submitted Tuesday 17 July 2018 @ 17:10:50 GMT
18 pages, 25 images

We present a novel photolithography based technique to efficiently fabricate microlens-fibre based Integral Field Units (IFUs). These IFUs are being developed for Devasthal Optical Telescope Integral Field Spectrograph (DOTIFS) which offer sixteen deployable IFUs. In each IFU, a 12 x 12 microlens array is matched with a similar array of fibres to better than +/- 5 micron accuracy for each microlens-fibre pair in the array. A mask created on copper foils using photolithography, transfer the pupil spot pattern of each microlens array to a fibre array holder. The approach can be used for mass production of IFUs in an extremely efficient and cost-effective manner.

[133] arXiv:1807.06561v1 [pdf, vox]

MOPSS I: Flat Optical Spectra for the Hot Jupiters WASP-4 b and WASP-52b

E. M. May, M. Zhao, M. Haidar, E. Rauscher, J. D. Monnier
Submitted Tuesday 17 July 2018 @ 17:10:49 GMT
21 pages, 16 figures, 4 tables. Accepted for publication in AJ

We present the first results from MOPSS, The Michigan Optical Planetary Spectra Survey, aimed at creating a database of optical planetary transmission spectra all observed, reduced, and analyzed with a uniform method for the benefit of enabling comparative exoplanet studies. We discuss our methods, and present results for our first two targets observed with the Magellan Baade 6.5m telescope, one transit of the Hot Jupiter WASP-4b and two transits of the Hot Saturn WASP-52b. Both targets present flat, featureless spectra, corresponding to the presence of aerosols. We find that the cloud decks must begin no lower than 10$^{-4}$ bar for both planets. For WASP-52b, we also consider the effects of star spots on the transmission spectrum, including unocculted spots and spots on the stellar limb influencing the light curve limb darkening parameters. We discuss the usefulness of this program in the coming James Webb Space Telescope era.

[134] arXiv:1807.06548v1 [pdf, vox]

Discovery of three new transiting hot Jupiters: WASP-161 b, WASP-163 b and WASP-170 b

K. Barkaoui, A. Burdanov, C. Hellier, M. Gillon, B. Smalley, P. F. L. Maxted, M. Lendl, A. H. M. J. Triaud, D. R. Anderson, J. McCormac, E. Jehin, Y. Almleaky, D. J. Armstrong, Z. Benkhaldoun, F. Bouchy, D. J. A. Brown, A. C. Cameron, A. Daassou, L. Delrez, E. Ducrot, E. Foxell, C. Murray, L. D. Nielsen, F. Pepe, D. Pollacco, F. J. Pozuelos, D. Queloz, D. Segransan, S. Udry, S. Thompson, R. G. West
Submitted Tuesday 17 July 2018 @ 16:54:59 GMT

We present the discovery by the WASP-South transit survey of three new transiting hot Jupiters, WASP-161 b, WASP-163 b and WASP-170 b. Follow-up radial velocities obtained with the Euler/CORALIE spectrograph and high-precision transit light curves obtained with the TRAPPIST-North, TRAPPIST-South, SPECULOOS-South, NITES, and Euler telescopes have enabled us to determine the masses and radii for these transiting exoplanets. WASP-161\,b completes an orbit around its $V=11.1$ F6V-type host star in 5.406 days, and has a mass and radius of $2.5\pm 0.2$$M_{Jup}$ and $1.14\pm 0.06$ $R_{Jup}$ respectively. WASP-163\,b has an orbital period of 1.609 days, a mass of $1.9\pm0.2$ $M_{Jup}$, and a radius of $1.2\pm0.1$ $R_{Jup}$. Its host star is a $V=12.5$ G8-type dwarf. WASP-170\,b is on a 2.344 days orbit around a G1V-type star of magnitude $V=12.8$. It has a mass of $1.7\pm0.2$ $M_{Jup}$ and a radius of $1.14\pm0.09$ $R_{Jup}$. Given their irradiations ($\sim10^9$ erg.s$^{-1}$.cm$^{-2​}$) and masses, the three new planets sizes are in good agreement with classical structure models of irradiated giant planets.

[135] arXiv:1807.06542v1 [pdf, vox]

Filamentary Structures and Star Formation Activities in the Sites S234, V582, and IRAS 05231+3512

L. K. Dewangan, T. Baug, D. K. Ojha, I. Zinchenko, A. Luna
Submitted Tuesday 17 July 2018 @ 16:47:47 GMT
28 pages, 18 figures, 2 tables, Accepted for publication in The Astrophysical Journal

To investigate the physical processes, we present observational results of the sites S234, V582, and IRAS 05231+3512 situated toward l = 171.7 - 174.1 degrees. Based on the CO line data, we find that these sites are not physically connected, and contain at least one filament (with length > 7 pc). The observed line masses (M_line,obs) of the filaments associated with V582 and IRAS 05231+3512 are ~37 and ~28 M_sun/pc, respectively. These filaments are characterized as thermally supercritical, and harbor several clumps. Groups of infrared-excess sources and massive B-type stars are observed toward the filament containing V582, while a very little star formation (SF) activity is found around IRAS 05231+3512. Our results favour radial collapse scenario in the filaments harboring V582 and IRAS 05231+3512. In the site S234, two filaments (i.e. ns1 (M_line,obs ~130 M_sun/pc) and ns2 (M_line,obs ~45 M_sun/pc)) are identified as thermally supercritical. An extended temperature structure at 27-30 K surrounds a relatively cold (~19 K) ~8.9 pc long filament ns1. At least four condensations (M_clump ~70-300 M_sun) are seen in ns1, and are devoid of the GMRT 610 MHz radio emission. The filament ns2 hosting clumps is devoid of ongoing SF, and could be at an early stage of fragmentation. An intense SF activity, having the SF efficiency ~3.3% and SF rate ~40-20 M_sun/Myr (for t_sf ~1-2 Myr), is observed in ns1. The feedback of massive stars in S234 seems to explain the observed SF in the filament ns1.

[136] arXiv:1807.05965v2 [pdf, vox]

The Cow: discovery of a luminous, hot and rapidly evolving transient

S. J. Prentice, K. Maguire, S. J. Smartt, M. R. Magee, P. Schady, S. Sim, T. -W. Chen, P. Clark, C. Colin, M. Fulton, O. McBrien, D. O`Neill, K. W. Smith, C. Ashall, K. C. Chambers, L. Denneau, H. A. Flewelling, A. Heinze, M. E. Huber, C. S. Kochanek, P. A. Mazzali, J. L. Prieto, A. Rest, B. J. Shappee, B. Stalder, K. Z. Stanek, M. D. Stritzinger, T. A. Thompson, J. L. Tonry
Submitted Tuesday 17 July 2018 @ 16:44:49 GMT
Submitted to ApJ Letters. Updated to reflect complete author list

We present the ATLAS discovery and initial analysis of the first 18 days of the unusual transient event, ATLAS18qqn/AT2018cow​. It is characeterized by a high peak luminosity ($\sim 1.7\times10^{44}$ erg s$^{-1}$), rapidly evolving light curves ($>$5 mag rise in $\sim$3 days), hot blackbody spectra, peaking at $\sim$27000 K that are relatively featureless and unchanging over the first two weeks. The bolometric light curve cannot be powered by radioactive decay under realistic assumptions. The detection of high-energy emission may suggest a central engine as the powering source. Using a magnetar model, we estimated an ejected mass of $0.1 - 0.4$ M$_\odot$, which lies between that of low-energy core-collapse events and the kilonova, AT2017gfo. The spectra of AT2018cow showed a number of shallow features overlying a blackbody continuum. The spectra cooled rapidly from 27000 to 15000 K in just over 2 weeks but the positions of shallow bumps in the spectra did not evolve, suggesting that they are produced in a shell or are potentially emission features. Using spectral modelling, we tentatively identify some features as being due to He I and He II and rule out that the features in the spectra are due to most elements up to and including the Fe-group. The presence of r-process elements cannot be ruled out. If these lines are due to He, then we suggest a low-mass star with residual He as a potential progenitor. Alternatively, models of magnetars formed in neutron-star mergers give plausible matches to the data.

[137] arXiv:1807.06593v1 [pdf, vox]

Black Hole Formation in the First Stellar Clusters

Harley Katz
Submitted Tuesday 17 July 2018 @ 16:06:08 GMT
Preprint of the chapter "Black Hole Formation in the First Stellar Clusters", to be published in the review volume "Formation of the First Black Holes", Latif, M. and Schleicher, D. R. G., eds., World Scientific Publishing Company, 2018, pp 125-143 [see https://www.worldsci​entific.com/worldsci​books/10.1142/10652]​

The early Universe was composed almost entirely of hydrogen and helium, with only trace amounts of heavy elements. It was only after the first generation of star formation that the Universe became sufficiently polluted to produce a second generation (Population II) of stars which are similar to those in our local Universe. Evidence of massive star cluster formation is nearly ubiquitous among the observed galaxy population and if this mode of star formation occurred at early enough epochs, the higher densities in the early Universe may have caused many of the stars in the cluster to strongly interact. In this scenario, it may be possible to form a very massive star by repeated stellar collisions that may directly collapse into a black hole and form a supermassive black hole seed. In this chapter, we will explore this scenario in detail to understand the dynamics which allow for this process to ensue and measure the probability for this type of seed to represent the supermassive black hole population observed at z > 6.

[138] arXiv:1807.06511v1 [pdf, vox]

Non-Unitary Evolution in the General Extended EFT of Inflation & Excited Initial States

Amjad Ashoorioon
Submitted Tuesday 17 July 2018 @ 15:51:11 GMT
1+21 pages, 2 figures

I study the "general" case that arises in the Extended Effective Field Theory of Inflation (gEEFToI), in which the coefficients of the sixth order polynomial dispersion relation depend on the physical wavelength of the fluctuation mode, hence they are time-dependent. At arbitrarily short wavelengths the unitarity is lost for each mode. Depending on the values of the gEEFToI parameters in the unitary gauge action, two scenarios can arise: in one, the coefficients of the polynomial become singular, flip signs at some physical wavelength and asymptote to a constant value as the wavelength of the mode is stretched to infinity. Starting from the WKB vacuum, the two-point function is essentially singular in the infinite IR limit. In the other case, the coefficients of the dispersion relation evolve monotonically from zero to a constant value in the infinite IR. In order to have a finite power spectrum starting from the vacuum in this case, the mode function has to be an eigensolution of the Confluent Heun (CH) equation, which leads to a very confined parameter space for gEEFToI. Finally, I look at a solution of the CH equation which is regular in the infinite IR limit and yields a finite power spectrum in either scenario. I demonstrate that this solution asymptotes to an excited state in past infinity in both cases. The result is interpreted in the light of the loss of unitarity for very small wavelengths. The outcome of such a non-unitary phase evolution should prepare each mode in the excited initial state that yields a finite two-point function for all the parameter space. This will be constraining of the new physics that UV completes such scenarios.

[139] arXiv:1807.06505v1 [pdf, vox]

X-ray Census of Millisecond Pulsars in the Galactic field

Jongsu Lee, C. Y. Hui, J. Takata, A. K. H. Kong, P. H. T. Tam, K. S. Cheng
Submitted Tuesday 17 July 2018 @ 15:41:21 GMT
19 pages, 12 figures, 4 tables, accepted for publication in ApJ

We have conducted a systematic survey for the X-ray properties of millisecond pulsars (MSPs). Currently, there are 47 MSPs with confirmed X-ray detections. We have also placed the upper limits for the X-ray emission from the other 36 MSPs by using the archival data. We have normalized their X-ray luminosities $L_{x}$ and their effective photon indices $\Gamma$ into a homogeneous data set, which enable us to carry out a detailed statistical analysis. Based on our censored sample, we report a relation of $L_{x}\simeq10^{31.0​5}\left(\dot{E}/10^{​35}\right)^{1.31}$ erg/s (2-10 keV) for the MSPs. The inferred X-ray conversion efficiency is found to be lower than previously reported estimate that could be affected by selection bias. $L_{x}$ also correlates/anti-corr​elates with the magnetic field strength at the light cylinder $B_{LC}$/characteris​tic age $\tau$. On the other hand, there is no correlation between $L_{x}$ and their surface magnetic field strength $B_{s}$. We have further divided the sample into four classes: (i) black-widows, (ii) redbacks, (iii) isolated MSPs and (iv) other MSP binaries, and compare the properties among them. We noted that while the rotational parameters and the orbital periods of redbacks and black-widow are similar, $L_{x}$ of redbacks are significantly higher than those of black-widows in the 2-10 keV band. Also the $\Gamma$ of redbacks are apparently smaller than those of black-widows, which indicates the X-ray emission of redbacks are harder than that of black-widows. This can be explained by the different contribution of intrabinary shocks in the X-ray emission of these two classes.

[140] arXiv:1807.06504v1 [pdf, vox]

Multimessenger Tests of Einstein's Weak Equivalence Principle and Lorentz Invariance with a High-energy Neutrino from a Flaring Blazar

Jun-Jie Wei, Bin-Bin Zhang, Lang Shao, He Gao, Ye Li, Qian-Qing Yin, Xue-Feng Wu, Xiang-Yu Wang, Bing Zhang, Zi-Gao Dai
Submitted Tuesday 17 July 2018 @ 15:33:12 GMT
5 pages, 1 table, no figures

The detection of the high-energy ($\sim290$ TeV) neutrino coincident with the flaring blazar TXS 0506+056, the first and only $3\sigma$ neutrino-source association to date, provides new, multimessenger tests of the weak equivalence principle (WEP) and Lorentz invariance. Assuming that the flight time difference between the TeV neutrino and gamma-ray photons from the blazar flare is mainly caused by the gravitational potential of the Laniakea supercluster of galaxies, we show that the deviation from the WEP for neutrinos and photons is conservatively constrained to be an accuracy of $10^{-6}-10^{-7}$, which is 3--4 orders of magnitude better than previous results placed by MeV neutrinos from supernova 1987A. In addition, we demonstrate that the association of the TeV neutrino with the blazar flare sets limits on the energy scale of quantum gravity for both linear and quadratic violations of Lorentz invariance (LIV) to $E_{\rm QG, 1}>3.2\times10^{15}-​3.7\times10^{16}$ GeV and $E_{\rm QG, 2}>4.0\times10^{10}-​1.4\times10^{11}$ GeV. These improve previous limits on both linear and quadratic LIV in neutrino propagation by 5--7 orders of magnitude.

[141] arXiv:1807.06496v1 [pdf, vox]

A Great Space Weather Event in February 1730

Hisashi Hayakawa, Yusuke Ebihara, José M. Vaquero, Kentaro Hattori, Víctor M. S. Carrasco, María de la Cruz Gallego, Satoshi Hayakawa, Yoshikazu Watanabe, Kiyomi Iwahashi, Harufumi Tamazawa, Akito D. Kawamura, Hiroaki Isobe
Submitted Tuesday 17 July 2018 @ 15:19:21 GMT
30 pages, 5 figures, and 2 tables, accepted for publication in Astronomy & Astrophysics on 25 April 2018. The figures and transcriptions/trans​lations of historical documents are partially omitted in this manuscript due to the condition of reproduction. They are available in the publisher version

Aims. Historical records provide evidence of extreme magnetic storms with equatorward auroral extensions before the epoch of systematic magnetic observations. One significant magnetic storm occurred on February 15, 1730. We scale this magnetic storm with auroral extension and contextualise it based on contemporary solar activity. Methods. We examined historical records in East Asia and computed the magnetic latitude (MLAT) of observational sites to scale magnetic storms. We also compared them with auroral records in Southern Europe. We examined contemporary sunspot observations to reconstruct detailed solar activity between 1729 and 1731. Results. We show 29 auroral records in East Asian historical documents and 37 sunspot observations. Conclusions. These records show that the auroral displays were visible at least down to 25.8{\deg} MLAT throughout East Asia. In comparison with contemporary European records, we show that the boundary of the auroral display closest to the equator surpassed 45.1{\deg} MLAT and possibly came down to 31.5{\deg} MLAT in its maximum phase, with considerable brightness. Contemporary sunspot records show an active phase in the first half of 1730 during the declining phase of the solar cycle. This magnetic storm was at least as intense as the magnetic storm in 1989, but less intense than the Carrington event.

[142] arXiv:1807.06492v1 [pdf, vox]

Vortex Formation and Survival in Protoplanetary Disks subject to Vertical Shear Instability

Natascha Manger, Hubert Klahr
Submitted Tuesday 17 July 2018 @ 15:17:05 GMT
Accepted for publication in MNRAS

Several protoplanetary disks observed by ALMA show dust concentrations consistent with particle trapping in giant vortices. The formation and survival of vortices is of major importance for planet formation, because vortices act as particle traps and are therefore preferred locations of planetesimal formation. Recent studies showed that the vertical shear instability (VSI) is capable of generating turbulence and small vortices in protoplanetary disks that have the proper radial and vertical stratification and thermally relax on sufficiently short time scales. But the effect of the azimuthal extend of the disk is often neglected as the disks azimuth is limited to $\Delta \phi \leq \pi/2$. We aim to investigate the influence of the azimuthal extent of the disk on the long-term evolution of a protoplanetary disk and the possibility of large vortices forming. To this end, we perform 3-dimensional simulations for up to 1000 local orbits using different values of $\Delta \phi = \pi/2 $ to $2\pi$ for VSI in disks with a prescribed radial density and temperature gradient cooling on short timescales. We find the VSI capable of forming large vortices which can exist at least several hundred orbits in simulations covering a disk with $\Delta \phi \geq \pi$. This suggests the VSI to be capable to form vortices or at least to trigger vortex formation via a secondary instability, e.g. Rossby Wave Instability or Kelvin Helmholtz Instability.

[143] arXiv:1807.06486v1 [pdf, vox]

Massive stars in the hinterland of the young cluster, Westerlund 2

J. E. Drew, A. Herrero, M. Mohr-Smith, M. Monguio, N. J. Wright, T. Kupfer, R. Napiwotzki
Submitted Tuesday 17 July 2018 @ 15:09:22 GMT
Accepted for publication in MNRAS, 13 July 2018. 16 pages, plus one-page table in an appendix

An unsettled question concerning the formation and distribution of massive stars is whether they must be born in massive clusters and, if found in less dense environments, whether they must have migrated there. With the advent of wide-area digital photometric surveys, it is now possible to identify massive stars away from prominent Galactic clusters without bias. In this study we consider 40 candidate OB stars found in the field around the young massive cluster, Westerlund 2, by Mohr-Smith et al (2017): these are located inside a box of 1.5x1.5 square degrees and are selected on the basis of their extinctions and K magnitudes. We present VLT/X-shooter spectra of two of the hottest O stars, respectively 11 and 22 arcmin from the centre of Westerlund 2. They are confirmed as O4V stars, with stellar masses likely to be in excess of 40 Msun. Their radial velocities relative to the non-binary reference object, MSP 182, in Westerlund 2 are -29.4 +/- 1.7 and -14.4 +/- 2.2 km/s, respectively. Using Gaia DR2 proper motions we find that between 8 and 11 early O/WR stars in the studied region (including the two VLT targets, plus WR 20c and WR 20aa) could have been ejected from Westerlund 2 in the last one million years. This represents an efficiency of massive-star ejection of up to 25%. On sky, the positions of these stars and their proper motions show a near N--S alignment. We discuss the possibility that these results are a consequence of prior sub-cluster merging combining with dynamical ejection.

[144] arXiv:1807.05318v2 [pdf, vox]

$Λ$CDM Predictions for the Satellite Population of M33

Ekta Patel, Jeffrey L. Carlin, Erik J. Tollerud, Michelle L. M. Collins, Gregory A. Dooley
Submitted Tuesday 17 July 2018 @ 15:09:04 GMT
15 pages, 3 figures, submitted to MNRAS

Triangulum (M33) is the most massive satellite galaxy of Andromeda (M31), with a stellar mass of about $3\times10^9\; M_{\odot}$. Based on abundance matching techniques, M33's total mass at infall is estimated to be of order $10^{11}\; M_{\odot}$. $\Lambda$CDM simulations predict that M33-mass halos host several of their own low mass satellite companions, yet only one candidate M33 satellite has been detected in deep photometric surveys to date. This `satellites of satellites' hierarchy has recently been explored in the context of the dwarf galaxies discovered around the Milky Way's Magellanic Clouds in the Dark Energy Survey. Here we discuss the number of satellite galaxies predicted to reside within the virial radius ($\sim$160 kpc) of M33 based on $\Lambda$CDM simulations. We also calculate the expected number of satellite detections in N fields of data using various ground--based imagers. Finally, we discuss how these satellite population predictions change as a function of M33's past orbital history. If M33 is on its first infall into M31's halo, its proposed satellites are expected to remain bound to M33 today. However, if M33 experienced a recent tidal interaction with M31, the number of surviving satellites depends strongly on the distance achieved at pericenter due to the effects of tidal stripping. We conclude that a survey extending to $\sim$100 kpc around M33 would be sufficient to constrain its orbital history and a majority of its satellite population. In the era of WFIRST, surveys of this size will be considered small observing programs.

[145] arXiv:1807.06482v1 [pdf, vox]

Axisymmetric, Rotating and Stratified Star

Mayer Humi
Submitted Tuesday 17 July 2018 @ 14:56:16 GMT
preprint. ALL comments or feedback will be appreciated

The paper considers Euler-Poisson equations which govern the steady state of a self gravitating, rotating, axi-symmetric stars under the additional assumption that it is composed of incompressible stratified fluid. The original system of six nonlinear equations is reduced to two equations, one for the mass density and the other for gravitational field. This reduction is carried out separately in cylindrical and spherical coordinates. As a "byproduct" we derive also expressions for the pressure. The resulting equations are then solved approximately and these analytic solutions are used then to determine the shape of the rotating star.

[146] arXiv:1807.05249v2 [pdf, vox]

VTXO - Virtual Telescope for X-Ray Observations

Kyle Rankin, Steven Stochaj, Neerav Shah, John Krizmanic, Asal Naseri
Submitted Tuesday 17 July 2018 @ 14:30:37 GMT
IWSCFF 2017

The Virtual Telescope for X-Ray Observations (VTXO) is a conceptual mission under development to demonstrate a new instrument for astronomical observations in the X-ray band using a set of 6U CubeSats. VTXO will use a Phase Fresnel Lens, which has the potential to improve the imaging resolution several orders of magnitude over the current state-of-the-art X-ray telescopes. This technique requires long focal lengths (>100 m), which necessitates the lens and camera be on separate spacecraft, flying in precision formation. This work presents the results from a model developed to determine the {\Delta}V requirements to maintain formation, for both solar and galactic X-ray observations, from a Geostationary Transfer Orbit.

[147] arXiv:1807.06460v1 [pdf, vox]

Long term X-ray variability characteristics of the narrow-line Seyfert 1 galaxy RE~J1034+396

K. Chaudhury, V. R. Chitnis, A. R. Rao, K. P. Singh, Sudip Bhattacharyya, G. C. Dewangan, S. Chakraborty, S. Chandra, G. C. Stewart, K. Mukerjee, R. K. Dey
Submitted Tuesday 17 July 2018 @ 14:19:19 GMT
8 pages, 9 figures, Published in MNRAS

We present the results of our study of the long term X-ray variability characteristics of the Narrow Line Seyfert 1 galaxy RE J1034+396. We use data obtained from the AstroSat satellite along with the light curves obtained from XMM-Newton and Swift-XRT. We use the 0.3 - 7.0 keV and 3 - 20 keV data, respectively, from the SXT and the LAXPC of AstroSat. The X-ray spectra in the 0.3 - 20 keV region are well fit with a model consisting of a power-law and a soft excess described by a thermal-Compton emission with a large optical depth, consistent with the earlier reported results. We have examined the X-ray light curves in the soft and hard X-ray bands of SXT and LAXPC, respectively, and find that the variability is slightly larger in the hard band. To investigate the variability characteristics of this source at different time scales, we have used X-ray light curves obtained from XMM-Newton data (200 s to 100 ks range) and Swift-XRT data (1 day to 100 day range) and find that there are evidences to suggest that the variability sharply increases at longer time scales. We argue that the mass of the black hole in RE J1034+396 is likely to be $\sim$3 $\times$ 10$^6$ M$_\odot$, based on the similarity of the observed QPO to the high frequency QPO seen in the Galactic black hole binary, GRS 1915+105.

[148] arXiv:1807.06437v1 [pdf, vox]

Estimating tidal deformability, moment of inertia, quadrupole moment of merger components of GW170817

Sajad A. Bhat, Debades Bandyopadhyay
Submitted Tuesday 17 July 2018 @ 13:56:50 GMT
19 pages, 9 Figures

Tidal deformability, moment of inertia and quadrupole moment of merger components of GW170817 are investigated using different equations of state (EoSs) involving nucleons, $\Lambda$ hyperons, quarks resulting in $2M_{\odot}$ neutron stars. This calculation is performed for low spin case. It is found from the computations of tidal deformability parameters that soft to moderately stiff equations of state are allowed by the 50\text{\%} and 90\text{\%} credible regions obtained from the gravitational wave observation of binary neutron star merger GW170817, whereas the stiffest hadron-quark EoSs which lie above the upper 90\text{\%} limit, are ruled out. Next moment of inertia and quadrupole moment are calculated for merger component masses (1.58, 1.18) M$_{\odot}$. It follows from the calculation that the upper bounds on moments of inertia of merger components might be constrained in the range $\sim 1-2 \times 10^{45}$ g cm$^2$. As masses and moments of inertia are known, it is possible to estimate the radii of merger components which are $\sim 13$ km. The upper bounds on quadrupole moments of the merger components are found to be 0.29-0.3 $\times 10^{43}$ g cm$^2$.

[149] arXiv:1807.06432v1 [pdf, vox]

4G: Pure fourth-order gravity

Shuxun Tian
Submitted Tuesday 17 July 2018 @ 13:50:54 GMT
9+3 pages, 1 figure, submitted to PRD

Einstein field equations are second-order differential equations. In this paper, we propose a new gravity theory with pure fourth-order field equations, which we call 4G for brevity. We discuss the applications of 4G in cosmology, gravitational waves, and local gravitational systems. 4G predicts the scale factor $a\propto t^{4/3}$ for the matter-dominated universe, and $a\propto t$ for the radiation-dominated universe. The former can explain the late-time acceleration without suffering from the coincidence and fine-tuning problems, while the latter can solve the horizon problem. 4G is a massless gravity, which means the speed of gravitational waves equals to the speed of light. Based on the discussions about exact vacuum solution and weak field approximation, we argue that Schwarzschild metric should be the real physical metric to describe solar system in 4G.

[150] arXiv:1807.06429v1 [pdf, vox]

A simple non-parametric method for resolving merged doublet emission: Insights into extreme outflow kinematics

Carolin Villforth, Tom L. Underwood, Mark Tolson, Nikhil Modha
Submitted Tuesday 17 July 2018 @ 13:45:16 GMT
Submitted to MNRAS

Doublet line emission is common in astronomical sources (e.g. [OIII], [OII], NaD, MgII). In many cases, complex kinematics in the emitting source can cause the doublet lines to merge, making characterisation of the source kinematics challenging. Here, we present a non-parametric method for resolving merged doublet emission when the line ratio is known. The method does not require fitting the data and is therefore fast and robust. It is also ideal for visualisation. We show that the method recovers line profiles of merged emission lines in simulated data. We also show, using simulated data and mathematical analysis, that the method does not significantly increase noise levels in the extracted lines, and is robust to background contamination. We demonstrate the strength of the method by applying it to strongly merged [OIII] 5007/4959 {\AA} in Active Galactic Nuclei (AGN). A python implementation of the method is provided in the Appendix.

[151] arXiv:1807.06395v1 [pdf, vox]

Revisiting the clustering of narrow-line AGN in the local Universe: Joint dependence on stellar mass and color

Lixin Wang, Cheng Li
Submitted Tuesday 17 July 2018 @ 12:59:05 GMT
17 pages, 14 figures, submitted to MNRAS

We investigate the clustering and dark halo properties for the narrow-line active galactic nuclei (AGN) in the SDSS, particularly examining the joint dependence on galaxy mass and color. AGN in galaxies with blue colors or massive red galaxies with M*>~10^{10.5}Msun are found to show almost identical clustering amplitudes at all scales to control galaxies of the same mass, color and structural parameters. This suggests AGN activity in blue galaxies or massive red galaxies is regulated by internal processes, with no correlation with environment. The antibias of AGN at scales between ~100kpc and a few Mpc, as found in Li et al. (2006) for the AGN as a whole, is observed only for the AGN hosted by galaxies with red colors and relatively low masses <10^{10.5}Msun. A simple halo model in which AGN are preferentially found at dark halo centers can reproduce the observational results, but requiring a mass-dependent central fraction which is a factor of ~4 higher than the fraction estimated from the SDSS group catalogue. The same group catalogue reveals that the host groups of AGN in red satellites tend to have lower halo masses than control galaxies, while the host groups of AGN in red centrals tend to form earlier, as indicated by a larger stellar mass gap between the two most massive galaxies in the groups. Our result implies that the mass assembly history of dark halos may play an additional role in the AGN activity in low-mass red galaxies.

[152] arXiv:1807.04922v2 [pdf, vox]

Luminosity Profiles of Prominent Stellar Halos

Hong Bae Ann, Hyeong Wook Park
Submitted Tuesday 17 July 2018 @ 12:56:16 GMT
16 pages, 9figures

We present a sample of 54 disk galaxies which have well developed extraplanar structures. We selected them using visual inspections from the color images of the Sloan Digital Sky Survey. Since the sizes of the extraplanar structures are comparable to the disks, they are considered as prominent stellar halos rather than large bulges. A single S\'ersic profile fitted to the surface brightness along the minor-axis of the disk shows a luminosity excess in the central regions for the majority of sample galaxies. This central excess is considered to be caused by the central bulge component. The mean S\'ersic index of the single component model is $1.1\pm0.9$. A double S\'ersic profile model that employs $n=1$ for the inner region, and varying $n$ for the outer region, provides a better fit than the single S\'ersic profile model. For a small fraction of galaxies, a S\'ersic profile fitted with $n=4$ for the inner region gives similar results. There is a weak tendency of increasing $n$ with increasing luminosity and central velocity dispersion, but there is no dependence on the local background density.

[153] arXiv:1807.06381v1 [pdf, vox]

Understanding the Reconstruction of the Biased Tracer

Xin Wang, Ue-Li Pen
Submitted Tuesday 17 July 2018 @ 12:29:50 GMT
9 pages, 4 figures

Recent development in the reconstruction of the large-scale structure (LSS) has seen significant improvement in restoring the linear baryonic acoustic oscillation (BAO) from at least the non-linear matter field. This outstanding performance is achieved by iteratively solving the Monge-Ampere equation of the mass conservation. However, this technique also relies on several assumptions that are not valid in reality, namely the longitudinal displacement, the absence of shell-crossing and homogeneous initial condition. In particular, the conservation equation of the tracers comprises the biasing information that breaks down the last assumption. Consequently, direct reconstruction would entangle the non-linear displacement with complicated bias parameters and further affect the BAO. In this paper, we formulate a theoretical model describing the reconstructed biased map by matching the tracer overdensity with an auxiliary fluid with vanishing initial perturbation. Regarding the performance of the reconstruction algorithm, we show that even though the shot noise is still the most significant limiting factors in a realistic survey, inappropriate treatment of the bias could also shift the reconstructed frame and therefore broaden the BAO peak. We suggest that, in principle, this bias-related BAO smearing effect could be used to independently self-calibrate the bias parameters.

[154] arXiv:1807.06377v1 [pdf, vox]

Weighing the two stellar components of the Galactic Bulge

M. Zoccali, E. Valenti, O. A. Gonzalez
Submitted Tuesday 17 July 2018 @ 12:20:23 GMT
6 pages, 4 figures, accepted for publication on A&A

Recent spectroscopic surveys of the Galactic bulge have unambiguously shown that the bulge contains two main components, that are best separated in their iron content, but also differ in spatial distribution, kinematics, and abundance ratios. The so-called metal poor (MP) component peaks at [Fe/H]~-0.4, while the metal rich (MR) one peaks at [Fe/H]$~+0.3. The total metallicity distribution function is therefore bimodal, with a dip at [Fe/H]~0. The relative fraction of the two components changes significantly across the bulge area. We provide, for the first time, the fractional contribution of the MP and MR stars to the stellar mass budget of the Galactic bulge, and its variation across the bulge area. We find that MP stars make up 48% of the total stellar mass of the bulge, within the region |l|<10, |b|<9.5, with the remaining 52% made up of MR stars. The latter dominate the mass budget at intermediate latitudes |b|~4, but become marginal in the outer bulge (|b|>8). The MP component is more axisymmetric than the MR one, and it is at least comparable, and possibly slightly dominant in the inner few degrees. As a result, the MP component, which does not follow the main bar, is not marginal in terms of the total mass budget as previously thought, and this new observational evidence must be included in bulge models. While the total radial velocity dispersion has a trend that follows the total stellar mass, when we examine the velocity dispersion of each component individually, we find that MP stars have higher velocity dispersion where they make up a smaller fraction of the stellar mass, and viceversa. This is due to the kinematical and spatial distribution of the two metallicity component being significantly different, as already discussed in the literature.

[155] arXiv:1807.06372v1 [pdf, vox]

Optimizing astrophotonic spatial reformatters using simulated on-sky performance

Theodoros Anagnos, Robert J. Harris, Mark K. Corrigan, Andrew P. Reeves, Matthew J. Townson, David G. MacLachlan, Robert R. Thomson, Tim J. Morris, Christian Schwab, Andreas Quirrenbach
Submitted Tuesday 17 July 2018 @ 12:07:06 GMT
Conference proceedings in SPIE 2018 Austin Texas

One of the most useful techniques in astronomical instrumentation is image slicing. It enables a spectrograph to have a more compact angular slit, whilst retaining throughput and increasing resolving power. Astrophotonic components like the photonic lanterns and photonic reformatters can be used to replace bulk optics used so far. This study investigates the performance of such devices using end-to-end simulations to approximate realistic on-sky conditions. It investigates existing components, tries to optimize their performance and aims to understand better how best to design instruments to maximize their performance. This work complements the recent work in the field and provides an estimation for the performance of the new components.

[156] arXiv:1807.06371v1 [pdf, vox]

Testing and Improving a Set of Morphological Predictors of Flaring Activity

Ioannis Kontogiannis, Manolis K. Georgoulis, Sung-Hong Park, Jordan A Guerra
Submitted Tuesday 17 July 2018 @ 12:06:13 GMT

Efficient prediction of solar flares relies on parameters that quantify the eruptive capability of solar active regions. Several such quantitative predictors have been proposed in the literature, inferred mostly from photospheric magnetograms and/or white-light observations. Two of them are the Ising energy and the sum of the total horizontal magnetic field gradient. The former has been developed from line-of-sight magnetograms, while the latter uses sunspot detections and characteristics, based on continuum images. Aiming to include these parameters in an automated prediction scheme, we test their applicability on regular photospheric magnetic field observations provided by the Helioseismic and Magnetic Imager (HMI) instrument onboard the Solar Dynamics Observatory (SDO). We test their efficiency as predictors of flaring activity on a representative sample of active regions and investigate possible modifications of these quantities. The Ising energy appears to be an efficient predictor, and the efficiency is even improved if it is modified to describe interacting magnetic partitions or sunspot umbrae. The sum of the horizontal magnetic field gradient appears to be slightly more promising than the three variations of the Ising energy we implement in this article. The new predictors are also compared with two very promising predictors: the effective connected magnetic field strength and the total unsigned non-neutralized current. Our analysis shows that the efficiency of morphological predictors depends on projection effects in a nontrivial way. All four new predictors are found useful for inclusion in an automated flare forecasting facility, such as the Flare Likelihood and Region Eruption Forecasting (FLARECAST), but their utility, among others, will ultimately be determined by the validation effort underway in the framework of the FLARECAST project.

[157] arXiv:1807.06369v1 [pdf, vox]

X-ray Swift observations of SN 2018cow

L. E. Rivera Sandoval, T. J. Maccarone, A. Corsi, P. J. Brown, D. Pooley, J. C. Wheeler
Submitted Tuesday 17 July 2018 @ 12:02:35 GMT
Submitted to MNRAS letters

Supernova (SN) 2018cow is an optical transient detected in the galaxy CGCG 137-068. It has been classified as a SN due to various characteristics in its optical spectra. The transient is also a bright X-ray source. We present results of the analysis of ~62ks of X-ray observations taken with the Neil Gehrels Swift Observatory over 27 days. We found a variable behavior in the 0.3-10keV X-ray light curve of SN 2018cow, with variability timescales of days. The observed X-ray variability could be due to the interaction between the SN ejecta and a non-uniform circum-stellar medium, perhaps related to previous mass ejections from a luminous-blue-variab​le-like progenitor.

[158] arXiv:1807.06368v1 [pdf, vox]

Planetary Nebulae distances in GAIA DR2

Stefan Kimeswenger, Daniela Barría
Submitted Tuesday 17 July 2018 @ 11:59:58 GMT
4 pages, 4 figures, accepted for publication in Astronomy & Astrophysics (Letter)

Context: Planetary Nebula distance scales often suffer for model dependent solutions. Model independent trigonometric parallaxes have been rare. Space based trigonometric parallaxes are now available for a larger sample using the second data release of GAIA. Aims: We aim to derive a high quality approach for selection criteria of trigonometric parallaxes for planetary nebulae and discuss possible caveats and restrictions in the use of this data release. Methods: A few hundred sources from previous distance scale surveys were manually cross identified with data from the second GAIA data release (DR2) as coordinate based matching does not work reliable. The data are compared with the results of previous distance scales and to the results of a recent similar study, which was using the first data release GAIA DR1. Results: While the few available previous ground based and HST trigonometric parallaxes match perfectly to the new data sets, older statistical distance scales, reaching larger distances, do show small systematic differences. Restricting to those central stars, were photometric colors of GAIA show a negligible contamination by the surrounding nebula, the difference is negligible for radio flux based statistical distances, while those derived from H-alpha surface brightness still show minor differences. The DR2 study significantly improves the previous recalibration of the statistical distance scales using DR1/TGAS.

[159] arXiv:1807.06967v1 [pdf, vox]

Probing the formation of the seeds of supermassive black holes with gravitational waves

Monica Colpi
Submitted Tuesday 17 July 2018 @ 11:53:55 GMT
Preprint of a review volume chapter to be published in Latiff, M., and Schleicher, D. entitled Probing the formation of the seeds of supermassive black holes with gravitational waves. Volume title: Formation of the First Black Holes, 2018. Copyright World Scientific Publishing Company - link - https://www.worldsci​entific.com/worldsci​books/10.1142/10652

The existence of black holes in the intermediate mass interval between one hundred and ten thousand solar masses, filling the gap between the stellar and the supermassive black holes is a key prediction to explain the origin of luminous QSOs at redshifts as large as seven. There is a sheer difficulty in forming giant black holes of billion suns in less than one billion years. This has led to the concept of seed black holes. They are high redshift intermediate mass black holes that formed during cosmic dawn. Seeds are a transient population, which later grew massive through episodes of accretion and mergers. In this chapter we explore the possibility of discovering seed black holes and track their growth across all cosmic epoch, by detecting the gravitational wave signal they emit at the time of their coalescence, when they pair to form close binaries. We show that the ESA LISA mission for the detection of low frequency gravitational waves will be paramount in granting this insight. Gravitational waves travel unimpeded through the cosmos and carry exquisite information on the masses and spins of the merging black holes. To this purpose we introduce key concepts on the gravitational wave emission from binaries, describing briefly their formation pathway during halo mergers and galaxy collisions.

[160] arXiv:1807.06364v1 [pdf, vox]

Analysis of the September $\varepsilon$-Persei​d outburst in 2013

J. M. Madiedo, J. Zamorano, J. M. Trigo-Rodriguez, J. L. Ortiz, J. A. Docobo, J. Izquierdo, J. Lacruz, P. P. Campo, M. Andrade, S. Pastor, J. A. de los Reyes, F. Ocaña, A. Sanchez de Miguel, P. Pujols
Submitted Tuesday 17 July 2018 @ 11:51:23 GMT
Accepted for publication in Monthly Notices of the Royal Astronomical Society on 16 July 2018

We analyze the outburst experienced by the September $\varepsilon$-Persei​d meteor shower on 9 September 2013. As a result of our monitoring the atmospheric trajectory of 60 multi-station events observed over Spain was obtained and accurate orbital data were derived from them. On the basis of these orbits, we have tried to determine the likely parent body of this meteoroid stream by employing orbital dissimilarity criteria. In addition, the emission spectra produced by two events belonging to this meteor shower were also recorded. The analysis of these spectra has provided information about the chemical nature of their progenitor meteoroids. We also present an estimation of the tensile strength for these particles.

[161] arXiv:1807.06355v1 [pdf, vox]

Evolution and Final Fates of Rapidly Accreting Supermassive Stars

Takashi Hosokawa
Submitted Tuesday 17 July 2018 @ 11:31:50 GMT
Preprint of the Chapter "Evolution and Final Fates of Rapidly Accreting Supermassive Stars", to be published in the review volume "Formation of the First Black Holes", Latif M. and Schleicher D.R.G., eds., World Scientific Publishing Company, 2018, pp. [see https://www.worldsci​entific.com/worldsci​books/10.1142/10652]​

The formation of supermassive stars (SMSs) is a possible pathway to seed supermassive black holes in the early universe. This chapter summarizes recent theoretical efforts to understand their evolution, highlighting effects of very rapid accretion at the rates of $\dot{M}_* \gtrsim 0.1~$M$_\odot$ yr$^{-1}$. Stellar evolution calculations predict that such an accreting SMS has a characteristic feature, i.e., a very large radius that monotonically increases as the stellar mass increases. The radius exceeds $7000$ R$_\odot$ (or $30$ AU) after the star accretes the gas of more than $10^3$ M$_\odot$. We show that the emergence of the "supergiant protostar" stage is a key for the formation of SMSs, because resulting radiative feedback against the accretion flow is substantially weakened during this stage. We also show that these SMSs end their lives while the accretion continues, and that their final fates vary with different accretion rates.

[162] arXiv:1807.06337v1 [pdf, vox]

Black hole formation via gas-dynamical processes

Muhammad A. Latif
Submitted Tuesday 17 July 2018 @ 10:55:58 GMT
Preprint of the chapter "Black hole formation via gas-dynamical processes ", to be published in the review volume "Formation of the First Black Holes", Latif, M. and Schleicher, D. R. G., eds., World Scientific Publishing Company, 2018, pp 1-22 [see https://www.worldsci​entific.com/worldsci​books/10.1142/10652]​

Understanding the formation of earliest supermassive black holes is a question of prime astrophysical interest. In this chapter, we focus on the formation of massive black holes via gas dynamical processes. The necessary requirement for this mechanism are large inflow rates of about 0.1 solar mass per year. We discuss how to obtain such inflow rates via an isothermal collapse in the presence of atomic hydrogen cooling, and the outcome of such a collapse from three dimensional cosmological simulations in subsection 2.2. Alternatives to an isothermal direct collapse are discussed in subsection 3 which include trace amounts of metals and/or molecular hydrogen. In the end, we briefly discuss future perspectives and potential detection of massive black hole seeds via upcoming missions.

[163] arXiv:1807.06335v1 [pdf, vox]

Gauge Field Mimetic Cosmology

Mohammad Ali Gorji, Shinji Mukohyama, Hassan Firouzjahi, Seyed Ali Hosseini Mansoori
Submitted Tuesday 17 July 2018 @ 10:54:07 GMT
21 pages

We extend the mimetic cosmology to models containing gauge invariant $p$-forms. The $0$-form case reproduces the well-known results of the mimetic dark matter, the $1$-form corresponds to the gauge field mimetic model while the $2$-form model is the Hodge dual of the $0$-form model in $4$ spacetime dimensions. We study the cosmological applications of the new gauge field mimetic model and show that it generates an energy density component which mimics the roles of spatial curvature. In the presence of the Maxwell term, the model also supports the flat, open and closed de Sitter-like cosmological backgrounds while the spatial geometry is flat for all three cases. We perform the cosmological perturbations analysis and show that the model is stable in the case of open de Sitter-like solution while it suffers from ghost instabilities in the case of the closed de Sitter-like solution.

[164] arXiv:1807.06334v1 [pdf, vox]

The magnetic field vector of the Sun-as-a-star. II. Evolution of the large-scale vector field through activity cycle 24

A. A. Vidotto, L. Lehmann, M. Jardine, A. Pevtsov
Submitted Tuesday 17 July 2018 @ 10:51:35 GMT
11 pages, 9 figures, 3 tables. Accepted to MNRAS

In the present work, we investigate how the large-scale magnetic field of the Sun, in its three vector components, has evolved during most of cycle 24, from 2010 Jan to 2018 Apr. To filter out the small-scale field of the Sun, present in high-resolution synoptic maps, we use a spherical harmonic decomposition method, which decomposes the solar field in multipoles with different l degrees. By summing together the low-l multipoles, we reconstruct the large-scale field at a resolution similar to observed stellar magnetic fields, which allows the direct comparison between solar and stellar magnetic maps. During cycle 24, the `Sun-as-a-star' magnetic field shows a polarity reversal in the radial and meridional components, but not in the azimuthal component. The large-scale solar field remains mainly poloidal with > 70% of its energy contained in the poloidal component. During its evolution, the large-scale field is more axisymmetric and more poloidal when near minima in sunspot numbers, and with a larger intensity near maximum. There is a correlation between toroidal energy and sunspot number, which indicates that spot fields are major contributors to the toroidal large-scale energy of the Sun. The solar large-scale magnetic properties fit smoothly with observational trends of stellar magnetism reported in See et al. The toroidal (Etor) and poloidal (Epol) energies are related as Etor ~Epol^{1.38 \pm 0.04}. Similar to the stellar sample, the large-scale field of the Sun shows a lack of toroidal non-axisymmetric field.

[165] arXiv:1807.06332v1 [pdf, vox]

When binaries keep track of recent nucleosynthesis: The Zr - Nb pair in extrinsic stars as an s-process diagnostic

D. Karinkuzhi, S. Van Eck, A. Jorissen, S. Goriely, L. Siess, T. Merle, A. Escorza, M. Van der Swaelmen, H. M. J. Boffin, T. Masseron, S. Shetye, B. Plez
Submitted Tuesday 17 July 2018 @ 10:46:02 GMT
25 pages, 20 figures, Accepted for publication in Astronomy and Astrophysics

Barium stars are s-process enriched giants. They owe their chemical peculiarities to a past mass transfer phase. During which they were polluted by their binary companion, which at the time was an AGB star, but is now an extinct white dwarf. Barium stars are thus ideal targets for understanding and constraining the s-process in low and intermediate-mass AGB stars. We derive the abundances of a large number of heavy elements in order to shed light on the conditions of operation of the neutron source responsible for the production of s-elements in the former companions of the barium stars. Adopting a recently used methodology(Neyskens et al. 2015), we analyse a sample of 18 highly enriched barium stars observed with the high-resolution HERMES spectrograph mounted on the MERCATOR telescope (La Palma). We determine the stellar parameters and abundances using MARCS model atmospheres. In particular, we derive the Nb/Zr ratio which was previously shown to be a sensitive thermometer for the s-process nucleosynthesis. Indeed, in barium stars, $^{93}Zr$ has fully decayed into mono-isotopic $^{93}Nb$ , so Nb/Zr is a measure of the temperature-sensitiv​e $^{93}Zr/Zr$ isotopic ratio. HD 28159, previously classified as K5III and initially selected to serve as a reference cool K star for our abundance analysis, turns out to be enriched in s-process elements, and as such is a new barium star. Four stars, characterised by high nitrogen abundances, also tend to have high [Nb/Zr] and [hs/ls] ratios. The derived Zr and Nb abundances provide more accurate constraints on the s-process neutron source, identified to be $^{13}C(alpha,n)^{16​}O$ for barium stars. The comparison with stellar evolution and nucleosynthesis models shows that the investigated barium stars were polluted by a low-mass (2-3 Solar mass) AGB star. HD 100503 is potentially identified as the highest metallicity CEMP-rs star yet discovered.

[166] arXiv:1807.06318v1 [pdf, vox]

HORST: Holographic Orbital Return Storage Technology

Matthias Raudonis, Natalia Triantafyllou, Anna Zhuravlova
Submitted Tuesday 17 July 2018 @ 10:23:05 GMT

Nowadays, space science is facing increasing problems with the amount of data collected from sensors in space and its transmission back to Earth. In this paper we introduce the novel Holographic Orbital Return Storage Technology (HORST) and its potential application in space industry. The proposed solution is a payload module which stores hundreds of terabytes of data on a robust 5D holographic disk. After the end of mission (EOM), the module is detached from the satellite and lowered into the Earth's atmosphere, protected by a heatshield surface and a parachute. The recovery of the module allows the readout of big sensor data on Earth. Besides fulfilling the big demand for applications of this technology nowadays, this paper discusses several major use-cases for near-future concepts and missions. HORST will enable many possibilities for new science missions and business in space. Since there is no comparable alternative technology, the lack of competition and the increasing demand will allow HORST to become a key technology for space.

[167] arXiv:1807.06313v1 [pdf, vox]

ELT HARMONI: Image Slicer Preliminary Design

Florence Laurent, Didier Boudon, Johan Kosmalski, Magali Loupias, Guillaume Raffault, Alban Remillieux, Niranjan Thatte, Ian Bryson, Hermine Schnetler, Fraser Clarke, Matthias Tecza
Submitted Tuesday 17 July 2018 @ 10:10:30 GMT
13 pages, 19 figures, 4 tables, Submitted to SPIE Astronomical Telescopes and Instrumentation

Harmoni is the ELT's first light visible and near-infrared integral field spectrograph. It will provide four different spatial scales, ranging from coarse spaxels of 60 x 30 mas best suited for seeing limited observations, to 4 mas spaxels that Nyquist sample the diffraction limited point spread function of the ELT at near-infrared wavelengths. Each spaxel scale may be combined with eleven spectral settings, that provide a range of spectral resolving powers from R 3500 to R 20000 and instantaneous wavelength coverage spanning the 0.47 - 2.45 {\mu}m wavelength range of the instrument. The consortium consists of several institutes in Europe under leadership of Oxford University. Harmoni is starting its Final Design Phase after a Preliminary Design Phase in November, 2017. The CRAL has the responsibility of the Integral Field Unit design linking the Preoptics to the 4 Spectrographs. It is composed of a field splitter associated with a relay system and an image slicer that create from a rectangular Field of View a very long (540mm) output slit for each spectrograph. In this paper, the preliminary design and performances of Harmoni Image Slicer will be presented including image quality, pupil distortion and slit geometry. It has been designed by CRAL for Harmoni PDR in November, 2017. Special emphases will be put on straylight analysis and slice diffraction. The optimisation of the manufacturing and slit geometry will also be reported.

[168] arXiv:1807.06310v1 [pdf, vox]

A high velocity component to the complex absorption in IRAS 13349+2438

M. L. Parker, G. A. Matzeu, M. Guainazzi, E. Kalfountzou, G. Miniutti, M. Santos-Lleó, N. Schartel
Submitted Tuesday 17 July 2018 @ 09:59:19 GMT
13 pages, 13 figures, accepted for publication in MNRAS

We present an analysis of XMM-Newton spectra of the low-redshift quasar IRAS 13349+2438. The RGS spectrum shows a large number of absorption lines from two zones of warm absorption, with velocities of $\sim$-600 km s$^{-1}$, as noted by previous authors. Additionally, we find robust evidence from multiple Ly{\alpha} absorption lines for a previously undiscovered ultra-fast zone of absorption, with an outflow velocity of $-0.13\pm0.01c$. The warm absorbers and ultra-fast outflow have similar mass outflow rates, around 40% of the Eddington accretion rate, but the kinetic power is dominated by the high velocity gas, which has a power of $\sim$4% of the Eddington luminosity.

[169] arXiv:1807.06297v1 [pdf, vox]

The Gaia-ESO Survey: the N/O abundance ratio in the Milky Way

L. Magrini, F. Vincenzo, S. Randich, E. Pancino, G. Casali, G. Tautvaisiene, A. Drazdauskas, S. Mikolaitis, R. Minkeviciute, E. Stonkute, Y. Chorniy, V. Bagdonas, G. Kordopatis, E. Frie, V. Roccatagliata, F. M. Jimenez-Esteban, G. Gilmore, A. Vallenari, T. Bensby, A. Bragaglia, A. J. Korn, A. C. Lanzafame, R. Smiljanic, A. Bayo, A. R. Casey, M. T. Costado, E. Franciosini, A. Hourihane, Jofré, J. Lewis, L. Monaco, L. Morbidelli, G. Sacco, C. Worley
Submitted Tuesday 17 July 2018 @ 09:32:36 GMT
9 pages, 7 figures (Appendix not available in the current version), accepted for publication on A&A

The abundance ratio N/O is a useful tool to study the interplay of galactic processes, e.g. star formation efficiency, time-scale of infall and outflow loading factor We aim to trace log(N/O) versus [Fe/H] in the Milky Way and to compare it with a set of chemical evolution models to understand the role of infall, outflow and star formation efficiency in the building-up of the Galactic disc. We use the abundances from idr2-3, idr4, idr5 data releases of the Gaia-ESO Survey both for Galactic field and open cluster stars.We determine membership and average composition of open clusters and we separate thin and thick disc field stars.We consider the effect of mixing in the abundance of N in giant stars. We compute a grid of chemical evolution models, suited to reproduce the main features of our Galaxy, exploring the effects of the star formation efficiency, the infall time-scale and the differential outflow. With our samples, we map the metallicity range -0.6<[Fe/H]<0.3 with a corresponding -1.2<log(N/O)<-0.2, where the secondary production of N dominates. Thanks to the wide range of Galactocentric distances covered by our samples, we can distinguish the behaviour of log(N/O) in different parts of the Galaxy. Our spatially resolved results allow us to distinguish differences in the evolution of N/O with Galactocentric radius. Comparing the data with our models, we can characterise the radial regions of our Galaxy. A shorter infall time-scale is needed in the inner regions, while the outer regions need a longer infall time-scale, coupled with a higher star formation efficiency. We compare our results with nebular abundances obtained in MaNGA galaxies, finding in our Galaxy a much wider range of log(N/O) than in integrated observations of external galaxies of similar stellar mass, but similar to the ranges found in studies of individual H ii regions.

[170] arXiv:1807.06296v1 [pdf, vox]

Black hole spin from wobbling and rotation of the M87 jet and a sign of a magnetically arrested disc

Denis Nikolaevich Sob'yanin
Submitted Tuesday 17 July 2018 @ 09:32:29 GMT
6 pages

New long-term Very Long Baseline Array observations of the well-known jet in the M87 radio galaxy at 43 GHz show that the jet experiences a sideways shift with an approximately 8-10 yr quasi-periodicity. Such jet wobbling can be indicative of a relativistic Lense-Thirring precession resulting from a tilted accretion disc. The wobbling period together with up-to-date kinematic data on jet rotation opens up the possibility for estimating angular momentum of the central supermassive black hole. In the case of a test-particle precession, the specific angular momentum is $J/Mc=(2.7\pm1.5)\ti​mes10^{14}$ cm, implying moderate dimensionless spin parameters $a=0.5\pm0.3$ and $0.31\pm0.17$ for controversial gas-dynamic and stellar-dynamic black hole masses. However, in the case of a solid-body-like precession, the spin parameter is much smaller for both masses, $0.15\pm0.05$. Rejecting this value on the basis of other independent spin estimations requires the existence of a magnetically arrested disc in M87.

[171] arXiv:1807.06281v1 [pdf, vox]

Design of a SiPM-based cluster for the Large Size Telescope camera of CTA

M. Mallamaci, B. Baibussinov, G. Busetto, D. Corti, A. De Angelis, F. Di Pierro, M. Doro, L. Lessio, M. Mariotti, E. Prandini, R. Rando, P. Vallania, C. F. Vigorito
Submitted Tuesday 17 July 2018 @ 08:51:07 GMT
submitted to NIM A

A Silicon Photomultiplier (SiPM)-based photodetector is being built to demonstrate its feasibility for an alternative silicon-based camera design for the Large Size Telescope (LST) of the Cherenkov Telescope Array. It has been designed to match the size of the standard Photomultiplier Tube (PMT) cluster unit and to be compatible with mechanics, electronics and focal plane optics of the first LST camera. Here, we describe the overall SiPM cluster design along with the main differences with respect to the currently used PMT cluster unit. The fast electronics of the SiPM pixel and its layout are also presented. In order to derive the best working condition for the final unit, we measured the SiPM performances in terms of gain, photo-detection efficiency and cross-talk. One pixel, a unit of 14 SiPMs, has been built. We will discuss also some preliminary results regarding this device and we will highlight the future steps of this project.

[172] arXiv:1807.06278v1 [pdf, vox]

Finite element analysis of the magnetic coupling to the Advanced Virgo payloads and its impact on the low frequency sensitivity

A. Cirone, A. Chincarini, M. Neri, S. Farinon, G. Gemme, I. Fiori, F. Paoletti, E. Majorana, P. Puppo, P. Rapagnani, P. Ruggi, B. L. Swinkels
Submitted Tuesday 17 July 2018 @ 08:39:23 GMT
12 pages, 11 figures

We study the electro-magnetic feedback of the Advanced Virgo (AdV) Input Mirror Payload (IMP), in response to a slowly time-varying magnetic field. As the problem is not amenable to analytical solution, we employ and validate a finite element (FE) analysis approach. The FE model is built to represent as faithfully as possible the real object and it has been validated by comparison with experimental measurements. The intent is to estimate the induced currents and the magnetic field in the neighbourhood of the payload. The procedure found 21 equivalent electrical configurations that are compatible with the measurements. These have been used to compute the magnetic noise contribution to the total AdV strain noise. At the current stage of development AdV seems to be unaffected by magnetic noise, but we foresee a non-negligible coupling once AdV reaches the design sensitivity.

[173] arXiv:1807.06269v1 [pdf, vox]

Formation of the First Black holes: Formation and evolution of the cosmic large-scale structure

Bjoern Malte Schaefer
Submitted Tuesday 17 July 2018 @ 08:10:59 GMT
chapter 2 of the review volume "Formation of the First Black Holes" compiled by M. Latif and D. Schleicher, to be published by World Scientific Publishing Company, 2018

The article is part of a review volume on the formation of the first black holes and summarises FLRW-cosmologies, the statistical description of cosmic structures as Gaussian random fields, as well as fluid mechanics in the linear and nonlinear regime. In particular, I review the evolution of the cosmic large-scale structure in linear structure formation and describe how perturbative solutions are constructed, leading to the built-up of non-Gaussianitites. Lastly, I discuss halo formation by spherical collapse and number densities of haloes that form in a Gaussian random field.

[174] arXiv:1807.06265v1 [pdf, vox]

Photospheric carbon, nitrogen, and oxygen abundances of A-type main-sequence stars

Yoichi Takeda, Satoshi Kawanomoto, Naoko Ohishi, Dong-Il Kang, Byeong-Cheol Lee, Kang-Min Kim, Inwoo Han
Submitted Tuesday 17 July 2018 @ 07:52:25 GMT
18 pages, 9 figures, 4 tables, 1 online data table, accepted for publication in Publ. Astron. Soc. Japan

Based on the spectrum fitting method applied to CI 5380, NI 7486, and OI 6156-8 lines, we determined the abundances of C, N, and O for 100 mostly A-type main-sequence stars (late B through early F at 11000K>Teff>7000K) comprising normal stars as well as non-magnetic chemically peculiar (CP) stars in the projected rotational velocity range of 0km/s<vsini<100km/s, where our aim was to investigate the abundance anomalies of these elements in terms of mutual correlation, dependence upon stellar parameters, and difference between normal and CP stars. We found that CNO are generally underabundant (relative to the standard star Procyon) typically by several tenths dex to ~1dex for almost all stars (regardless of CP or normal), though those classified as peculiar (Am or HgMn) tend to show larger underabundance, especially for C in late Am stars and for N in HgMn stars of late B-type, for which deficiency amounts even up to ~2dex. While the behaviors of these three elements are qualitatively similar to each other, the quantitative extent of peculiarity (or the vulnerability to the physical process causing anomaly) tends to follow the inequality relation of C>N>O. Regarding the considerable star-to-star dispersion observed at any Teff, the most important cause is presumably the difference in rotational velocity. These observational facts appear to be more or less favorably compared with the recent theoretical calculations based on the model of atomic diffusion and envelope mixing.

[175] arXiv:1807.06590v1 [pdf, vox]

Clusters of primordial black holes

Konstantin M. Belotsky, Vyacheslav I. Dokuchaev, Yury N. Eroshenko, Ekaterina A. Esipova, Maxim Yu. Khlopov, Leonid A. Khromykh, Alexander A. Kirillov, Valeriy V. Nikulin, Sergey G. Rubin, Igor V. Svadkovsky
Submitted Tuesday 17 July 2018 @ 07:34:47 GMT
40 pages, 16 figures

The Primordial Black Holes (PBHs) are gradually involved into consideration as the phenomenon having reliable basis. We discuss here the possibility of their agglomeration into clusters that may have several prominent observable features. The clusters can form due to closed domain walls appearance in the natural and the hybrid inflation with subsequent evolution and gravitational collapse. Early dustlike stages of dominance of heavy metastable dissipative particles, at which star-like objects are formed, can also naturally lead to formation of black hole clusters, remaining in the Universe after decay of particles, from which they have originated. The dynamical evolution of such clusters discussed here is of the crucial importance. Such a model inherits all the advantages of the single PBHs like possible explanation of existence of supermassive black holes (origin of the early quasars), binary BH merges registered by LIGO/Virgo through gravitational waves, contribution to reionization of the Universe, but also has additional benefits. The cluster could alleviate or completely avoid existing constraints on the single PBH abundance making PBHs a real dark matter candidate. The most of existing constraints on (single) PBH density should be re-considered as applied to the clusters. Also unidentified cosmic gamma-ray point-like sources could be (partially) accounted for by them. One can conclude, that it seems really to be much more viable model with respect to the single PBHs.

[176] arXiv:1807.06248v1 [pdf, vox]

Formation of the first stars

Ralf S. Klessen
Submitted Tuesday 17 July 2018 @ 06:56:15 GMT
Preprint of chapter 4 "Formation of the first stars", to be published in the review volume "Formation of the first black holes", Latif, M. and Schleicher, D. R. G., eds., World Scientific Publishing Company, 2018, pages 67 - 98 [see https://www.worldsci​entific.com/worldsci​books/10.1142/10652]​

From studying the cosmic microwave background, we know our Universe started out very simple. It was by and large homogeneous and isotropic, with small fluctuations that can be described by linear perturbation theory. In stark contrast, the Universe today is highly structured on a vast range of length and mass scales. In the evolution towards increasing complexity, the formation of the first stars marks a primary transition event. The first generation of stars, the so-called Population III (or Pop. III) build up from truly metal-free primordial gas. They have long been thought to live short, solitary lives, with only one massive star forming per halo. However, in recent years this simple picture has undergone substantial revision, and we now understand that stellar birth in the early Universe is subject to the same complexity as star formation at present days. In this chapter, I review the current state of the field. I begin by introducing the basics concepts of star-formation theory and by discussing the typical environment in which Pop. III stars are thought to form. Then I argue that the accretion disk that builds up in the center of a halo is likely to fragment, resulting in the formation of a cluster of stars with a wide range of masses, and I speculate about how this process may be influenced by stellar feedback, the presence of magnetic fields, the energy input from dark matter annihilation, and the occurrence of large- scale streaming velocities between baryons and dark matter. Finally, I discuss direct and indirect constraints on Pop. III star formation from high-redshift observations and from the search for extremely metal-poor stars in the Milky Way and its satellites.

[177] arXiv:1807.06246v1 [pdf, vox]

Relationships between HI Gas Mass, Stellar Mass and Star Formation Rate of HICAT+WISE (HI-WISE) Galaxies

Vaishali Parkash, Micheal J. I. Brown, T. H. Jarrett, Nicolas J. Bonne
Submitted Tuesday 17 July 2018 @ 06:49:51 GMT
20 pages, 13 figures; accepted for publication by ApJ

We have measured the relationships between HI mass, stellar mass and star formation rate using the HI Parkes All Sky-Survey Catalogue (HICAT) and the Wide-field Infrared Survey Explorer (WISE). Of the 3,513 HICAT sources, we find 3.4 micron counterparts for 2,896 sources (80%) and provide new WISE matched aperture photometry for these galaxies. For our principal sample of spiral galaxies with W1 $\le$ 10 mag and z $\le$ 0.01, we identify HI detections for 93% of the sample. We measure lower HI-stellar mass relationships that HI selected samples that do not include spiral galaxies with little HI gas. Our observations of the spiral sample show that HI mass increases with stellar mass with a power-law index 0.35; however, this value is dependent on T-type, which affects both the median and the dispersion of HI mass. We also observe an upper limit on the HI gas fraction, which is consistent with a halo spin parameter model. We measure the star formation efficiency of spiral galaxies to be constant 10$^{-9.57}$ yr$^{-1}$ $\pm$ 0.4 dex for 2.5 orders of magnitude in stellar mass, despite the higher stellar mass spiral showing evidence of quenched star formation.

[178] arXiv:1807.06243v1 [pdf, vox]

Super-Eddington accretion; flow regimes and conditions in high-z galaxies

Lucio Mayer
Submitted Tuesday 17 July 2018 @ 06:41:58 GMT
Preprint of the chapter "Super-Eddington accretion; flow regimes and conditions in high-z galaxies", to be published in the review volume "Formation of the First Black Holes", Latif, M. and Schleicher, D. R. G., eds., World Scientific Publishing Company, 2018, pp 195-228 [ see https://www.worldsci​entific.com/worldsci​books/10.1142/10652 ]

We review and discuss theoretical studies addressing the possibility of gas accretion onto black holes occurring at rates exceeding the Eddington limit. Our focus is on the applications to the growth of black hole seeds at high redshift. We first present the general notion of Super-Eddington accretion, and then summarize the different models and numerical simulations developed to study such regime. We consider optically thick flows in accretion disks as well as in spherically symmetric envelopes, and devote particular attention to the widely adopted model based on the SLIM disk solution. While attractive for its simplicity, the SLIM disk solution is challenged by the latest generation of three-dimensional radiation (magneto)-hydrodynam​ical simulations, in which radiative losses can be an order of magnitude higher, and the mechanisms of radiation transport is more complex than straight advection as it takes place in a complex turbulent regime. We then discuss the gas supply rate to the sub-pc scale accretion disk or envelope from larger scales, revisiting gas inflow rates in protogalaxies under various conditions. We conclude that in the dense gaseous nuclei of high-z galaxies the conditions necessary for the onset of Super Eddington accretion regimes, such as a high optical depth and high gas supply rates from large scales, should be naturally met. Feedback from the growing BH seed should not alter significantly such conditions according to the results of radiation magneto-hydrodynamic​al simulations of super-critical flows in accretion disks. Furthermore, based on the required nuclear gas inflow rates and the tendency of stellar feedback to remove efficiently gas in low mass halos, we argue that super-critical accretion will be more easily achieved in relatively sizable halos, with virial masses $M_{\rm vir} > 10^{10}$ M$_{\odot}$, which become more common at $z < 15$.

[179] arXiv:1807.06225v1 [pdf, vox]

Stationary bound-state massive scalar field configurations supported by spherically symmetric compact reflecting stars

Shahar Hod
Submitted Tuesday 17 July 2018 @ 05:03:59 GMT
9 pages

It has recently been demonstrated that asymptotically flat neutral reflecting stars are characterized by an intriguing no-hair property. In particular, it has been proved that these {\it horizonless} compact objects cannot support spatially regular {\it static} matter configurations made of scalar (spin-0) fields, vector (spin-1) fields, and tensor (spin-2) fields. In the present paper we shall explicitly prove that spherically symmetric compact reflecting stars can support {\it stationary} (rather than static) bound-state massive scalar fields in their exterior spacetime regions. To this end, we solve analytically the Klein-Gordon wave equation for a linearized scalar field of mass $\mu$ and proper frequency $\omega$ in the curved background of a spherically symmetric compact reflecting star of mass $M$ and radius $R_{\text{s}}$. It is proved that the regime of existence of these stationary composed star-field configurations is characterized by the simple inequalities $1-2M/R_{\text{s}}<(​\omega/\mu)^2<1$. Interestingly, in the regime $M/R_{\text{s}}\ll1$ of weakly self-gravitating stars we derive a remarkably compact {\it analytical} formula for the discrete spectrum $\{\omega(M,R_{\text​{s}},\mu)\}^{n=\inft​y}_{n=1}$ of resonant oscillation frequencies which characterize the stationary composed compact-reflecting-s​tar-linearized-massi​ve-scalar-field configurations. Finally, we verify the accuracy of the analytically derived resonance formula of the composed star-field configurations with direct numerical computations.

[180] arXiv:1807.06221v1 [pdf, vox]

Prospects for Detecting the First Black Holes with the Next Generation of Telescopes

Mark Dijkstra
Submitted Tuesday 17 July 2018 @ 04:51:55 GMT
Preprint of the chapter "Prospects for Detecting the First Black Holes with the Next Generation of Telescopes", to be published in the review volume "Formation of the First Black Holes", Latif, M. and Schleicher, D. R. G., eds., World Scientific Publishing Company, 2018, pp 269-288 [see https://www.worldsci​entific.com/worldsci​books/10.1142/10652]​

This chapter describes the prospects for detecting the first black holes in our Universe, with a specific focus on instruments/telescop​es that will come online within the next decade, including e.g. the SKA, WFIRST, EUCLID, JWST, and large ground-based facilities such as E-ELTs, GMT and TMT. This chapter focusses on: (1) the indirect detectability of the first generations of stellar mass black holes through their imprint on various Cosmic Background Radiation fields including the 21-cm and X-ray backgrounds; (2) direct detectability of line and continuum emission by more massive black holes (M_BH ~ 1e4-1e6 M_sun) that formed via channels other than `ordinary' stellar evolution.

[181] arXiv:1807.06212v1 [pdf, vox]

Planck 2018 results. XII. Galactic astrophysics using polarized dust emission

Planck Collaboration, N. Aghanim, Y. Akrami, M. I. R. Alves, M. Ashdown, J. Aumont, C. Baccigalupi, M. Ballardini, A. J. Banday, R. B. Barreiro, N. Bartolo, S. Basak, K. Benabed, J. -P. Bernard, M. Bersanelli, P. Bielewicz, J. J. Bock, J. R. Bond, J. Borrill, F. R. Bouchet, F. Boulanger, A. Bracco, M. Bucher, C. Burigana, E. Calabrese, J. -F. Cardoso, J. Carron, R. -R. Chary, H. C. Chiang, L. P. L. Colombo, C. Combet, B. P. Crill, F. Cuttaia, P. de Bernardis, G. de Zotti, J. Delabrouille, J. -M. Delouis, E. Di Valentino, C. Dickinson, J. M. Diego, O. Doré, M. Douspis, A. Ducout, X. Dupac, G. Efstathiou, F. Elsner, T. A. Enßlin, H. K. Eriksen, Y. Fantaye, R. Fernandez-Cobos, K. Ferrière, F. Forastieri, M. Frailis, A. A. Fraisse, E. Franceschi, A. Frolov, S. Galeotta, S. Galli, K. Ganga, R. T. Génova-Santos, M. Gerbino, T. Ghosh, J. González-Nuevo, K. M. Górski, S. Gratton, G. Green, A. Gruppuso, J. E. Gudmundsson, V. Guillet, W. Handley, F. K. Hansen, G. Helou, D. Herranz, E. Hivon, Z. Huang, A. H. Jaffe, W. C. Jones, E. Keihänen, R. Keskitalo, K. Kiiveri, J. Kim, N. Krachmalnicoff, M. Kunz, H. Kurki-Suonio, G. Lagache, J. -M. Lamarre, A. Lasenby, M. Lattanzi, C. R. Lawrence, M. Le Jeune, F. Levrier, M. Liguori, P. B. Lilje, V. Lindholm, M. López-Caniego, P. M. Lubin, Y. -Z. Ma, J. F. Macías-Pérez, G. Maggio, D. Maino, N. Mandolesi, A. Mangilli, A. Marcos-Caballero, M. Maris, P. G. Martin, E. Martínez-González, S. Matarrese, N. Mauri, J. D. McEwen, A. Melchiorri, A. Mennella, M. Migliaccio, M. -A. Miville-Deschênes, D. Molinari, A. Moneti, L. Montier, G. Morgante, A. Moss, P. Natoli, L. Pagano, D. Paoletti, G. Patanchon, F. Perrotta, V. Pettorino, F. Piacentini, L. Polastri, G. Polenta, J. -L. Puget, J. P. Rachen, M. Reinecke, M. Remazeilles, A. Renzi, I. Ristorcelli, G. Rocha, C. Rosset, G. Roudier, J. A. Rubiño-Martín, B. Ruiz-Granados, L. Salvati, M. Sandri, M. Savelainen, D. Scott, C. Sirignano, R. Sunyaev, A. -S. Suur-Uski, J. A. Tauber, D. Tavagnacco, M. Tenti, L. Toffolatti, M. Tomasi, T. Trombetti, J. Valiviita, B. Van Tent, P. Vielva, F. Villa, N. Vittorio, B. D. Wandelt, I. K. Wehus, A. Zacchei, A. Zonca
Submitted Tuesday 17 July 2018 @ 04:05:10 GMT

We present 353 GHz full-sky maps of the polarization fraction $p$, angle $\psi$, and dispersion of angles $S$ of Galactic dust thermal emission produced from the 2018 release of Planck data. We confirm that the mean and maximum of $p$ decrease with increasing $N_H$. The uncertainty on the maximum polarization fraction, $p_\mathrm{max}=22.0​$% at 80 arcmin resolution, is dominated by the uncertainty on the zero level in total intensity. The observed inverse behaviour between $p$ and $S$ is interpreted with models of the polarized sky that include effects from only the topology of the turbulent Galactic magnetic field. Thus, the statistical properties of $p$, $\psi$, and $S$ mostly reflect the structure of the magnetic field. Nevertheless, we search for potential signatures of varying grain alignment and dust properties. First, we analyse the product map $S \times p$, looking for residual trends. While $p$ decreases by a factor of 3--4 between $N_H=10^{20}$ cm$^{-2}$ and $N_H=2\times 10^{22}$ cm$^{-2}$, $S \times p$ decreases by only about 25%, a systematic trend observed in both the diffuse ISM and molecular clouds. Second, we find no systematic trend of $S \times p$ with the dust temperature, even though in the diffuse ISM lines of sight with high $p$ and low $S$ tend to have colder dust. We also compare Planck data with starlight polarization in the visible at high latitudes. The agreement in polarization angles is remarkable. Two polarization emission-to-extincti​on ratios that characterize dust optical properties depend only weakly on $N_H$ and converge towards the values previously determined for translucent lines of sight. We determine an upper limit for the polarization fraction in extinction of 13%, compatible with the $p_\mathrm{max}$ observed in emission. These results provide strong constraints for models of Galactic dust in diffuse gas.

[182] arXiv:1807.06211v1 [pdf, vox]

Planck 2018 results. X. Constraints on inflation

Planck Collaboration, Y. Akrami, F. Arroja, M. Ashdown, J. Aumont, C. Baccigalupi, M. Ballardini, A. J. Banday, R. B. Barreiro, N. Bartolo, S. Basak, K. Benabed, J. -P. Bernard, M. Bersanelli, P. Bielewicz, J. J. Bock, J. R. Bond, J. Borrill, F. R. Bouchet, F. Boulanger, M. Bucher, C. Burigana, R. C. Butler, E. Calabrese, J. -F. Cardoso, J. Carron, A. Challinor, H. C. Chiang, L. P. L. Colombo, C. Combet, D. Contreras, B. P. Crill, F. Cuttaia, P. de Bernardis, G. de Zotti, J. Delabrouille, J. -M. Delouis, E. Di Valentino, J. M. Diego, S. Donzelli, O. Doré, M. Douspis, A. Ducout, X. Dupac, S. Dusini, G. Efstathiou, F. Elsner, T. A. Enßlin, H. K. Eriksen, Y. Fantaye, J. Fergusson, R. Fernandez-Cobos, F. Finelli, F. Forastieri, M. Frailis, E. Franceschi, A. Frolov, S. Galeotta, S. Galli, K. Ganga, C. Gauthier, R. T. Génova-Santos, M. Gerbino, T. Ghosh, J. González-Nuevo, K. M. Górski, S. Gratton, A. Gruppuso, J. E. Gudmundsson, J. Hamann, W. Handley, F. K. Hansen, D. Herranz, E. Hivon, D. C. Hooper, Z. Huang, A. H. Jaffe, W. C. Jones, E. Keihänen, R. Keskitalo, K. Kiiveri, J. Kim, T. S. Kisner, N. Krachmalnicoff, M. Kunz, H. Kurki-Suonio, G. Lagache, J. -M. Lamarre, A. Lasenby, M. Lattanzi, C. R. Lawrence, M. Le Jeune, J. Lesgourgues, F. Levrier, A. Lewis, M. Liguori, P. B. Lilje, V. Lindholm, M. Lpez-Caniego, P. M. Lubin, Y. -Z. Ma, J. F. Macías-Pérez, G. Maggio, D. Maino, N. Mandolesi, A. Mangilli, A. Marcos-Caballero, M. Maris, P. G. Martin, E. Martínez-González, S. Matarrese, N. Mauri, J. D. McEwen, P. D. Meerburg, P. R. Meinhold, A. Melchiorri, A. Mennella, M. Migliaccio, S. Mitra, M. -A. Miville-Deschênes, D. Molinari, A. Moneti, L. Montier, G. Morgante, A. Moss, M. Münchmeyer, P. Natoli, H. U. Nørgaard-Nielsen, L. Pagano, D. Paoletti, B. Partridge, G. Patanchon, H. V. Peiris, F. Perrotta, V. Pettorino, F. Piacentini, L. Polastri, G. Polenta, J. -L. Puget, J. P. Rachen, M. Reinecke, M. Remazeilles, A. Renzi, G. Rocha, C. Rosset, G. Roudier, J. A. Rubiño-Martín, B. Ruiz-Granados, L. Salvati, M. Sandri, M. Savelainen, D. Scott, E. P. S. Shellard, M. Shiraishi, C. Sirignano, G. Sirri, L. D. Spencer, R. Sunyaev, A. -S. Suur-Uski, J. A. Tauber, D. Tavagnacco, M. Tenti, L. Toffolatti, M. Tomasi, T. Trombetti, J. Valiviita, B. Van Tent, P. Vielva, F. Villa, N. Vittorio, B. D. Wandelt, I. K. Wehus, S. D. M. White, A. Zacchei, J. P. Zibin, A. Zonca
Submitted Tuesday 17 July 2018 @ 04:05:09 GMT

We report on the implications for cosmic inflation of the 2018 Release of the Planck CMB anisotropy measurements. The results are fully consistent with the two previous Planck cosmological releases, but have smaller uncertainties thanks to improvements in the characterization of polarization at low and high multipoles. Planck temperature, polarization, and lensing data determine the spectral index of scalar perturbations to be $n_\mathrm{s}=0.9649​\pm 0.0042$ at 68% CL and show no evidence for a scale dependence of $n_\mathrm{s}.$ Spatial flatness is confirmed at a precision of 0.4% at 95% CL with the combination with BAO data. The Planck 95% CL upper limit on the tensor-to-scalar ratio, $r_{0.002}<0.10$, is further tightened by combining with the BICEP2/Keck Array BK14 data to obtain $r_{0.002}<0.064$. In the framework of single-field inflationary models with Einstein gravity, these results imply that: (a) slow-roll models with a concave potential, $V" (\phi) < 0,$ are increasingly favoured by the data; and (b) two different methods for reconstructing the inflaton potential find no evidence for dynamics beyond slow roll. Non-parametric reconstructions of the primordial power spectrum consistently confirm a pure power law. A complementary analysis also finds no evidence for theoretically motivated parameterized features in the Planck power spectrum, a result further strengthened for certain oscillatory models by a new combined analysis that includes Planck bispectrum data. The new Planck polarization data provide a stringent test of the adiabaticity of the initial conditions. The polarization data also provide improved constraints on inflationary models that predict a small statistically anisotropic quadrupolar modulation of the primordial fluctuations. However, the polarization data do not confirm physical models for a scale-dependent dipolar modulation.

[183] arXiv:1807.06210v1 [pdf, vox]

Planck 2018 results. VIII. Gravitational lensing

Planck Collaboration, N. Aghanim, Y. Akrami, M. Ashdown, J. Aumont, C. Baccigalupi, M. Ballardini, A. J. Banday, R. B. Barreiro, N. Bartolo, S. Basak, K. Benabed, J. -P. Bernard, M. Bersanelli, P. Bielewicz, J. J. Bock, J. R. Bond, J. Borrill, F. R. Bouchet, F. Boulanger, M. Bucher, C. Burigana, E. Calabrese, J. -F. Cardoso, J. Carron, A. Challinor, H. C. Chiang, L. P. L. Colombo, C. Combet, B. P. Crill, F. Cuttaia, P. de Bernardis, G. de Zotti, J. Delabrouille, E. Di Valentino, J. M. Diego, O. Doré, M. Douspis, A. Ducout, X. Dupac, G. Efstathiou, F. Elsner, T. A. Enßlin, H. K. Eriksen, Y. Fantaye, R. Fernandez-Cobos, F. Forastieri, M. Frailis, A. A. Fraisse, E. Franceschi, A. Frolov, S. Galeotta, S. Galli, K. Ganga, R. T. Génova-Santos, M. Gerbino, T. Ghosh, J. González-Nuevo, K. M. Górski, S. Gratton, A. Gruppuso, J. E. Gudmundsson, J. Hamann, W. Handley, F. K. Hansen, D. Herranz, E. Hivon, Z. Huang, A. H. Jaffe, W. C. Jones, A. Karakci, E. Keihänen, R. Keskitalo, K. Kiiveri, J. Kim, L. Knox, N. Krachmalnicoff, M. Kunz, H. Kurki-Suonio, G. Lagache, J. -M. Lamarre, A. Lasenby, M. Lattanzi, C. R. Lawrence, M. Le Jeune, F. Levrier, A. Lewis, M. Liguori, P. B. Lilje, V. Lindholm, M. López-Caniego, P. M. Lubin, Y. -Z. Ma, J. F. Macías-Pérez, G. Maggio, D. Maino, N. Mandolesi, A. Mangilli, A. Marcos-Caballero, M. Maris, P. G. Martin, E. Martínez-González, S. Matarrese, N. Mauri, J. D. McEwen, A. Melchiorri, A. Mennella, M. Migliaccio, M. -A. Miville-Deschênes, D. Molinari, A. Moneti, L. Montier, G. Morgante, A. Moss, P. Natoli, L. Pagano, D. Paoletti, B. Partridge, G. Patanchon, F. Perrotta, V. Pettorino, F. Piacentini, L. Polastri, G. Polenta, J. -L. Puget, J. P. Rachen, M. Reinecke, M. Remazeilles, A. Renzi, G. Rocha, C. Rosset, G. Roudier, J. A. Rubiño-Martín, B. Ruiz-Granados, L. Salvati, M. Sandri, M. Savelainen, D. Scott, C. Sirignano, R. Sunyaev, A. -S. Suur-Uski, J. A. Tauber, D. Tavagnacco, M. Tenti, L. Toffolatti, M. Tomasi, T. Trombetti, J. Valiviita, B. Van Tent, P. Vielva, F. Villa, N. Vittorio, B. D. Wandelt, I. K. Wehus, M. White, S. D. M. White, A. Zacchei, A. Zonca
Submitted Tuesday 17 July 2018 @ 04:05:08 GMT
Submitted to A&A. Abstract abridged for arxiv submission. Lensing data products available at https://wiki.cosmos.​esa.int/planck-legac​y-archive/index.php/​Lensing

We present measurements of the cosmic microwave background (CMB) lensing potential using the final $\textit{Planck}$ 2018 temperature and polarization data. We increase the significance of the detection of lensing in the polarization maps from $5\,\sigma$ to $9\,\sigma$. Combined with temperature, lensing is detected at $40\,\sigma$. We present an extensive set of tests of the robustness of the lensing-potential power spectrum, and construct a minimum-variance estimator likelihood over lensing multipoles $8 \le L \le 400$. We find good consistency between lensing constraints and the results from the $\textit{Planck}$ CMB power spectra within the $\rm{\Lambda CDM}$ model. Combined with baryon density and other weak priors, the lensing analysis alone constrains $\sigma_8 \Omega_{\rm m}^{0.25}=0.589\pm 0.020$ ($1\,\sigma$ errors). Also combining with baryon acoustic oscillation (BAO) data, we find tight individual parameter constraints, $\sigma_8=0.811\pm0.​019$, $H_0=67.9_{-1.3}^{+1​.2}\,\text{km}\,\tex​t{s}^{-1}\,\rm{Mpc}^​{-1}$, and $\Omega_{\rm m}=0.303^{+0.016}_{-​0.018}$. Combining with $\textit{Planck}$ CMB power spectrum data, we measure $\sigma_8$ to better than $1\,\%$ precision, finding $\sigma_8=0.811\pm 0.006$. We find consistency with the lensing results from the Dark Energy Survey, and give combined lensing-only parameter constraints that are tighter than joint results using galaxy clustering. Using $\textit{Planck}$ cosmic infrared background (CIB) maps we make a combined estimate of the lensing potential over $60\,\%$ of the sky with considerably more small-scale signal. We demonstrate delensing of the $\textit{Planck}$ power spectra, detecting a maximum removal of $40\,\%$ of the lensing-induced power in all spectra. The improvement in the sharpening of the acoustic peaks by including both CIB and the quadratic lensing reconstruction is detected at high significance (abridged).

[184] arXiv:1807.06209v1 [pdf, vox]

Planck 2018 results. VI. Cosmological parameters

Planck Collaboration, N. Aghanim, Y. Akrami, M. Ashdown, J. Aumont, C. Baccigalupi, M. Ballardini, A. J. Banday, R. B. Barreiro, N. Bartolo, S. Basak, R. Battye, K. Benabed, J. -P. Bernard, M. Bersanelli, P. Bielewicz, J. J. Bock, J. R. Bond, J. Borrill, F. R. Bouchet, F. Boulanger, M. Bucher, C. Burigana, R. C. Butler, E. Calabrese, J. -F. Cardoso, J. Carron, A. Challinor, H. C. Chiang, J. Chluba, L. P. L. Colombo, C. Combet, D. Contreras, B. P. Crill, F. Cuttaia, P. de Bernardis, G. de Zotti, J. Delabrouille, J. -M. Delouis, E. Di Valentino, J. M. Diego, O. Doré, M. Douspis, A. Ducout, X. Dupac, S. Dusini, G. Efstathiou, F. Elsner, T. A. Enßlin, H. K. Eriksen, Y. Fantaye, M. Farhang, J. Fergusson, R. Fernandez-Cobos, F. Finelli, F. Forastieri, M. Frailis, E. Franceschi, A. Frolov, S. Galeotta, S. Galli, K. Ganga, R. T. Génova-Santos, M. Gerbino, T. Ghosh, J. González-Nuevo, K. M. Górski, S. Gratton, A. Gruppuso, J. E. Gudmundsson, J. Hamann, W. Handley, D. Herranz, E. Hivon, Z. Huang, A. H. Jaffe, W. C. Jones, A. Karakci, E. Keihänen, R. Keskitalo, K. Kiiveri, J. Kim, T. S. Kisner, L. Knox, N. Krachmalnicoff, M. Kunz, H. Kurki-Suonio, G. Lagache, J. -M. Lamarre, A. Lasenby, M. Lattanzi, C. R. Lawrence, M. Le Jeune, P. Lemos, J. Lesgourgues, F. Levrier, A. Lewis, M. Liguori, P. B. Lilje, M. Lilley, V. Lindholm, M. López-Caniego, P. M. Lubin, Y. -Z. Ma, J. F. Macías-Pérez, G. Maggio, D. Maino, N. Mandolesi, A. Mangilli, A. Marcos-Caballero, M. Maris, P. G. Martin, M. Martinelli, E. Martínez-González, S. Matarrese, N. Mauri, J. D. McEwen, P. R. Meinhold, A. Melchiorri, A. Mennella, M. Migliaccio, M. Millea, S. Mitra, M. -A. Miville-Deschênes, D. Molinari, L. Montier, G. Morgante, A. Moss, P. Natoli, H. U. Nørgaard-Nielsen, L. Pagano, D. Paoletti, B. Partridge, G. Patanchon, H. V. Peiris, F. Perrotta, V. Pettorino, F. Piacentini, L. Polastri, G. Polenta, J. -L. Puget, J. P. Rachen, M. Reinecke, M. Remazeilles, A. Renzi, G. Rocha, C. Rosset, G. Roudier, J. A. Rubiño-Martín, B. Ruiz-Granados, L. Salvati, M. Sandri, M. Savelainen, D. Scott, E. P. S. Shellard, C. Sirignano, G. Sirri, L. D. Spencer, R. Sunyaev, A. -S. Suur-Uski, J. A. Tauber, D. Tavagnacco, M. Tenti, L. Toffolatti, M. Tomasi, T. Trombetti, L. Valenziano, J. Valiviita, B. Van Tent, L. Vibert, P. Vielva, F. Villa, N. Vittorio, B. D. Wandelt, I. K. Wehus, M. White, S. D. M. White, A. Zacchei, A. Zonca
Submitted Tuesday 17 July 2018 @ 04:05:07 GMT
71 pages. Parameter tables and chains available at https://wiki.cosmos.​esa.int/planck-legac​y-archive/index.php/​Cosmological_Paramet​ers

We present cosmological parameter results from the final full-mission Planck measurements of the CMB anisotropies. We find good consistency with the standard spatially-flat 6-parameter $\Lambda$CDM cosmology having a power-law spectrum of adiabatic scalar perturbations (denoted "base $\Lambda$CDM" in this paper), from polarization, temperature, and lensing, separately and in combination. A combined analysis gives dark matter density $\Omega_c h^2 = 0.120\pm 0.001$, baryon density $\Omega_b h^2 = 0.0224\pm 0.0001$, scalar spectral index $n_s = 0.965\pm 0.004$, and optical depth $\tau = 0.054\pm 0.007$ (in this abstract we quote $68\,\%$ confidence regions on measured parameters and $95\,\%$ on upper limits). The angular acoustic scale is measured to $0.03\,\%$ precision, with $100\theta_*=1.0411\​pm 0.0003$. These results are only weakly dependent on the cosmological model and remain stable, with somewhat increased errors, in many commonly considered extensions. Assuming the base-$\Lambda$CDM cosmology, the inferred late-Universe parameters are: Hubble constant $H_0 = (67.4\pm 0.5)$km/s/Mpc; matter density parameter $\Omega_m = 0.315\pm 0.007$; and matter fluctuation amplitude $\sigma_8 = 0.811\pm 0.006$. We find no compelling evidence for extensions to the base-$\Lambda$CDM model. Combining with BAO we constrain the effective extra relativistic degrees of freedom to be $N_{\rm eff} = 2.99\pm 0.17$, and the neutrino mass is tightly constrained to $\sum m_\nu< 0.12$eV. The CMB spectra continue to prefer higher lensing amplitudes than predicted in base -$\Lambda$CDM at over $2\,\sigma$, which pulls some parameters that affect the lensing amplitude away from the base-$\Lambda$CDM model; however, this is not supported by the lensing reconstruction or (in models that also change the background geometry) BAO data. (Abridged)

[185] arXiv:1807.06208v1 [pdf, vox]

Planck 2018 results. IV. Diffuse component separation

Planck Collaboration, Y. Akrami, M. Ashdown, J. Aumont, C. Baccigalupi, M. Ballardini, A. J. Banday, R. B. Barreiro, N. Bartolo, S. Basak, K. Benabed, M. Bersanelli, P. Bielewicz, J. R. Bond, J. Borrill, F. R. Bouchet, F. Boulanger, M. Bucher, C. Burigana, E. Calabrese, J. -F. Cardoso, J. Carron, B. Casaponsa, A. Challinor, L. P. L. Colombo, C. Combet, B. P. Crill, F. Cuttaia, P. de Bernardis, A. de Rosa, G. de Zotti, J. Delabrouille, J. -M. Delouis, E. Di Valentino, C. Dickinson, J. M. Diego, S. Donzelli, O. Doré, A. Ducout, X. Dupac, G. Efstathiou, F. Elsner, T. A. Enßlin, H. K. Eriksen, E. Falgarone, R. Fernandez-Cobos, F. Finelli, F. Forastieri, M. Frailis, A. A. Fraisse, E. Franceschi, A. Frolov, S. Galeotta, S. Galli, K. Ganga, R. T. Génova-Santos, M. Gerbino, T. Ghosh, J. González-Nuevo, K. M. Górski, S. Gratton, A. Gruppuso, J. E. Gudmundsson, W. Handley, F. K. Hansen, G. Helou, D. Herranz, Z. Huang, A. H. Jaffe, A. Karakci, E. Keihänen, R. Keskitalo, K. Kiiveri, J. Kim, T. S. Kisner, N. Krachmalnicoff, M. Kunz, H. Kurki-Suonio, G. Lagache, J. -M. Lamarre, A. Lasenby, M. Lattanzi, C. R. Lawrence, M. Le Jeune, F. Levrier, M. Liguori, P. B. Lilje, V. Lindholm, M. López-Caniego, P. M. Lubin, Y. -Z. Ma, J. F. Macías-Pérez, G. Maggio, D. Maino, N. Mandolesi, A. Mangilli, A. Marcos-Caballero, P. G. Martin, E. Martínez-González, S. Matarrese, N. Mauri, J. D. McEwen, P. R. Meinhold, A. Melchiorri, A. Mennella, M. Migliaccio, M. -A. Miville-Deschênes, D. Molinari, A. Moneti, L. Montier, G. Morgante, P. Natoli, F. Oppizzi, L. Pagano, D. Paoletti, B. Partridge, M. Peel, V. Pettorino, F. Piacentini, G. Polenta, J. -L. Puget, J. P. Rachen, M. Reinecke, M. Remazeilles, A. Renzi, G. Rocha, G. Roudier, J. A. Rubiño-Martín, B. Ruiz-Granados, L. Salvati, M. Sandri, M. Savelainen, D. Scott, D. S. Seljebotn, C. Sirignano, L. D. Spencer, A. -S. Suur-Uski, J. A. Tauber, D. Tavagnacco, M. Tenti, H. Thommesen, L. Toffolatti, M. Tomasi, T. Trombetti, J. Valiviita, B. Van Tent, P. Vielva, F. Villa, N. Vittorio, B. D. Wandelt, I. K. Wehus, A. Zacchei, A. Zonca
Submitted Tuesday 17 July 2018 @ 04:05:06 GMT
74 pages, submitted to A&A

We present full-sky maps of the cosmic microwave background (CMB) and polarized synchrotron and thermal dust emission, derived from the third set of Planck frequency maps. These products have significantly lower contamination from instrumental systematic effects than previous versions. The methodologies used to derive these maps follow closely those described in earlier papers, adopting four methods (Commander, NILC, SEVEM, and SMICA) to extract the CMB component, as well as three methods (Commander, GNILC, and SMICA) to extract astrophysical components. Our revised CMB temperature maps agree with corresponding products in the Planck 2015 delivery, whereas the polarization maps exhibit significantly lower large-scale power, reflecting the improved data processing described in companion papers; however, the noise properties of the resulting data products are complicated, and the best available end-to-end simulations exhibit relative biases with respect to the data at the few percent level. Using these maps, we are for the first time able to fit the spectral index of thermal dust independently over 3 degree regions. We derive a conservative estimate of the mean spectral index of polarized thermal dust emission of beta_d = 1.55 +/- 0.05, where the uncertainty marginalizes both over all known systematic uncertainties and different estimation techniques. For polarized synchrotron emission, we find a mean spectral index of beta_s = -3.1 +/- 0.1, consistent with previously reported measurements. We note that the current data processing does not allow for construction of unbiased single-bolometer maps, and this limits our ability to extract CO emission and correlated components. The foreground results for intensity derived in this paper therefore do not supersede corresponding Planck 2015 products. For polarization the new results supersede the corresponding 2015 products in all respects.

[186] arXiv:1807.06207v1 [pdf, vox]

Planck 2018 results. III. High Frequency Instrument data processing and frequency maps

Planck Collaboration, N. Aghanim, Y. Akrami, M. Ashdown, J. Aumont, C. Baccigalupi, M. Ballardini, A. J. Banday, R. B. Barreiro, N. Bartolo, S. Basak, K. Benabed, J. -P. Bernard, M. Bersanelli, P. Bielewicz, J. R. Bond, J. Borrill, F. R. Bouchet, F. Boulanger, M. Bucher, C. Burigana, E. Calabrese, J. -F. Cardoso, J. Carron, A. Challinor, H. C. Chiang, L. P. L. Colombo, C. Combet, F. Couchot, B. P. Crill, F. Cuttaia, P. de Bernardis, A. de Rosa, G. de Zotti, J. Delabrouille, J. -M. Delouis, E. Di Valentino, J. M. Diego, O. Doré, M. Douspis, A. Ducout, X. Dupac, G. Efstathiou, F. Elsner, T. A. Enßlin, H. K. Eriksen, E. Falgarone, Y. Fantaye, F. Finelli, M. Frailis, A. A. Fraisse, E. Franceschi, A. Frolov, S. Galeotta, S. Galli, K. Ganga, R. T. Génova-Santos, M. Gerbino, T. Ghosh, J. González-Nuevo, K. M. Górski, S. Gratton, A. Gruppuso, J. E. Gudmundsson, W. Handley, F. K. Hansen, S. Henrot-Versillé, D. Herranz, E. Hivon, Z. Huang, A. H. Jaffe, W. C. Jones, A. Karakci, E. Keihänen, R. Keskitalo, K. Kiiveri, J. Kim, T. S. Kisner, N. Krachmalnicoff, M. Kunz, H. Kurki-Suonio, G. Lagache, J. -M. Lamarre, A. Lasenby, M. Lattanzi, C. R. Lawrence, F. Levrier, M. Liguori, P. B. Lilje, V. Lindholm, M. López-Caniego, Y. -Z. Ma, J. F. Macías-Pérez, G. Maggio, D. Maino, N. Mandolesi, A. Mangilli, P. G. Martin, E. Martínez-González, S. Matarrese, N. Mauri, J. D. McEwen, A. Melchiorri, A. Mennella, M. Migliaccio, M. -A. Miville-Deschênes, D. Molinari, A. Moneti, L. Montier, G. Morgante, A. Moss, S. Mottet, P. Natoli, L. Pagano, D. Paoletti, B. Partridge, G. Patanchon, L. Patrizii, O. Perdereau, F. Perrotta, V. Pettorino, F. Piacentini, J. -L. Puget, J. P. Rachen, M. Reinecke, M. Remazeilles, A. Renzi, G. Rocha, G. Roudier, L. Salvati, M. Sandri, M. Savelainen, D. Scott, C. Sirignano, G. Sirri, L. D. Spencer, R. Sunyaev, A. -S. Suur-Uski, J. A. Tauber, D. Tavagnacco, M. Tenti, L. Toffolatti, M. Tomasi, M. Tristram, T. Trombetti, J. Valiviita, F. Vansyngel, B. Van Tent, L. Vibert, P. Vielva, F. Villa, N. Vittorio, B. D. Wandelt, I. K. Wehus, A. Zonca
Submitted Tuesday 17 July 2018 @ 04:05:05 GMT
Accepted for publication on A&A (AA/2018/32909)

This paper presents the High Frequency Instrument (HFI) data processing procedures for the Planck 2018 release. Major improvements in mapmaking have been achieved since the previous 2015 release. They enabled the first significant measurement of the reionization optical depth parameter using HFI data. This paper presents an extensive analysis of systematic effects, including the use of simulations to facilitate their removal and characterize the residuals. The polarized data, which presented a number of known problems in the 2015 Planck release, are very significantly improved. Calibration, based on the CMB dipole, is now extremely accurate and in the frequency range 100 to 353 GHz reduces intensity-to-polariz​ation leakage caused by calibration mismatch. The Solar dipole direction has been determined in the three lowest HFI frequency channels to within one arc minute, and its amplitude has an absolute uncertainty smaller than $0.35\mu$K, an accuracy of order $10^{-4}$. This is a major legacy from the HFI for future CMB experiments. The removal of bandpass leakage has been improved by extracting the bandpass-mismatch coefficients for each detector as part of the mapmaking process; these values in turn improve the intensity maps. This is a major change in the philosophy of "frequency maps", which are now computed from single detector data, all adjusted to the same average bandpass response for the main foregrounds. Simulations reproduce very well the relative gain calibration of detectors, as well as drifts within a frequency induced by the residuals of the main systematic effect. Using these simulations, we measure and correct the small frequency calibration bias induced by this systematic effect at the $10^{-4}$ level. There is no detectable sign of a residual calibration bias between the first and second acoustic peaks in the CMB channels, at the $10^{-3}$ level.

[187] arXiv:1807.06206v1 [pdf, vox]

Planck 2018 results. II. Low Frequency Instrument data processing

Planck Collaboration, Y. Akrami, F. Argüeso, M. Ashdown, J. Aumont, C. Baccigalupi, M. Ballardini, A. J. Banday, R. B. Barreiro, N. Bartolo, S. Basak, K. Benabed, J. -P. Bernard, M. Bersanelli, P. Bielewicz, L. Bonavera, J. R. Bond, J. Borrill, F. R. Bouchet, F. Boulanger, M. Bucher, C. Burigana, R. C. Butler, E. Calabrese, J. -F. Cardoso, L. P. L. Colombo, B. P. Crill, F. Cuttaia, P. de Bernardis, A. de Rosa, G. de Zotti, J. Delabrouille, E. Di Valentino, C. Dickinson, J. M. Diego, S. Donzelli, A. Ducout, X. Dupac, G. Efstathiou, F. Elsner, T. A. Enßlin, H. K. Eriksen, Y. Fantaye, F. Finelli, M. Frailis, E. Franceschi, A. Frolov, S. Galeotta, S. Galli, K. Ganga, R. T. Génova-Santos, M. Gerbino, T. Ghosh, J. González-Nuevo, K. M. Górski, S. Gratton, A. Gruppuso, J. E. Gudmundsson, W. Handley, F. K. Hansen, D. Herranz, E. Hivon, Z. Huang, A. H. Jaffe, W. C. Jones, A. Karakci, E. Keihänen, R. Keskitalo, K. Kiiveri, J. Kim, T. S. Kisner, N. Krachmalnicoff, M. Kunz, H. Kurki-Suonio, J. -M. Lamarre, A. Lasenby, M. Lattanzi, C. R. Lawrence, J. P. Leahy, F. Levrier, M. Liguori, P. B. Lilje, V. Lindholm, M. López-Caniego, Y. -Z. Ma, J. F. Macías-Pérez, G. Maggio, D. Maino, N. Mandolesi, A. Mangilli, M. Maris, P. G. Martin, E. Martínez-González, S. Matarrese, N. Mauri, J. D. McEwen, P. R. Meinhold, A. Melchiorri, A. Mennella, M. Migliaccio, D. Molinari, L. Montier, G. Morgante, A. Moss, P. Natoli, L. Pagano, D. Paoletti, B. Partridge, G. Patanchon, L. Patrizii, M. Peel, F. Perrotta, V. Pettorino, F. Piacentini, G. Polenta, J. -L. Puget, J. P. Rachen, B. Racine, M. Reinecke, M. Remazeilles, A. Renzi, G. Rocha, G. Roudier, J. A. Rubiño-Martín, L. Salvati, M. Sandri, M. Savelainen, D. Scott, D. S. Seljebotn, C. Sirignano, G. Sirri, L. D. Spencer, A. -S. Suur-Uski, J. A. Tauber, D. Tavagnacco, M. Tenti, L. Terenzi, L. Toffolatti, M. Tomasi, T. Trombetti, J. Valiviita, F. Vansyngel, B. Van Tent, P. Vielva, F. Villa, N. Vittorio, B. D. Wandelt, R. Watson, I. K. Wehus, A. Zacchei, A. Zonca
Submitted Tuesday 17 July 2018 @ 04:05:04 GMT

We present a final description of the data-processing pipeline for the Planck, Low Frequency Instrument (LFI), implemented for the 2018 data release. Several improvements have been made with respect to the previous release, especially in the calibration process and in the correction of instrumental features such as the effects of nonlinearity in the response of the analogue-to-digital converters. We provide a brief pedagogical introduction to the complete pipeline, as well as a detailed description of the important changes implemented. Self-consistency of the pipeline is demonstrated using dedicated simulations and null tests. We present the final version of the LFI full sky maps at 30, 44, and 70 GHz, both in temperature and polarization, together with a refined estimate of the Solar dipole and a final assessment of the main LFI instrumental parameters.

[188] arXiv:1807.06205v1 [pdf, vox]

Planck 2018 results. I. Overview and the cosmological legacy of Planck

Planck Collaboration, Y. Akrami, F. Arroja, M. Ashdown, J. Aumont, C. Baccigalupi, M. Ballardini, A. J. Banday, R. B. Barreiro, N. Bartolo, S. Basak, R. Battye, K. Benabed, J. -P. Bernard, M. Bersanelli, P. Bielewicz, J. J. Bock, J. R. Bond, J. Borrill, F. R. Bouchet, F. Boulanger, M. Bucher, C. Burigana, R. C. Butler, E. Calabrese, J. -F. Cardoso, J. Carron, B. Casaponsa, A. Challinor, H. C. Chiang, L. P. L. Colombo, C. Combet, D. Contreras, B. P. Crill, F. Cuttaia, P. de Bernardis, G. de Zotti, J. Delabrouille, J. -M. Delouis, F. -X. Désert, E. Di Valentino, C. Dickinson, J. M. Diego, S. Donzelli, O. Doré, M. Douspis, A. Ducout, X. Dupac, G. Efstathiou, F. Elsner, T. A. Enßlin, H. K. Eriksen, E. Falgarone, Y. Fantaye, J. Fergusson, R. Fernandez-Cobos, F. Finelli, F. Forastieri, M. Frailis, E. Franceschi, A. Frolov, S. Galeotta, S. Galli, K. Ganga, R. T. Génova-Santos, M. Gerbino, T. Ghosh, J. González-Nuevo, K. M. Górski, S. Gratton, A. Gruppuso, J. E. Gudmundsson, J. Hamann, W. Handley, F. K. Hansen, G. Helou, D. Herranz, E. Hivon, Z. Huang, A. H. Jaffe, W. C. Jones, A. Karakci, E. Keihänen, R. Keskitalo, K. Kiiveri, J. Kim, T. S. Kisner, L. Knox, N. Krachmalnicoff, M. Kunz, H. Kurki-Suonio, G. Lagache, J. -M. Lamarre, M. Langer, A. Lasenby, M. Lattanzi, C. R. Lawrence, M. Le Jeune, J. P. Leahy, J. Lesgourgues, F. Levrier, A. Lewis, M. Liguori, P. B. Lilje, M. Lilley, V. Lindholm, M. López-Caniego, P. M. Lubin, Y. -Z. Ma, J. F. Macías-Pérez, G. Maggio, D. Maino, N. Mandolesi, A. Mangilli, A. Marcos-Caballero, M. Maris, P. G. Martin, E. Martínez-González, S. Matarrese, N. Mauri, J. D. McEwen, P. D. Meerburg, P. R. Meinhold, A. Melchiorri, A. Mennella, M. Migliaccio, M. Millea, S. Mitra, M. -A. Miville-Deschênes, D. Molinari, A. Moneti, L. Montier, G. Morgante, A. Moss, S. Mottet, M. Münchmeyer, P. Natoli, H. U. Nørgaard-Nielsen, C. A. Oxborrow, L. Pagano, D. Paoletti, B. Partridge, G. Patanchon, T. J. Pearson, M. Peel, H. V. Peiris, F. Perrotta, V. Pettorino, F. Piacentini, L. Polastri, G. Polenta, J. -L. Puget, J. P. Rachen, M. Reinecke, M. Remazeilles, A. Renzi, G. Rocha, C. Rosset, G. Roudier, J. A. Rubiño-Martín, B. Ruiz-Granados, L. Salvati, M. Sandri, M. Savelainen, D. Scott, E. P. S. Shellard, M. Shiraishi, C. Sirignano, G. Sirri, L. D. Spencer, R. Sunyaev, A. -S. Suur-Uski, J. A. Tauber, D. Tavagnacco, M. Tenti, L. Terenzi, L. Toffolatti, M. Tomasi, T. Trombetti, J. Valiviita, B. Van Tent, L. Vibert, P. Vielva, F. Villa, N. Vittorio, B. D. Wandelt, I. K. Wehus, M. White, S. D. M. White, A. Zacchei, A. Zonca
Submitted Tuesday 17 July 2018 @ 04:05:03 GMT
61 pages, 40 figures

The European Space Agency's Planck satellite, which was dedicated to studying the early Universe and its subsequent evolution, was launched on 14 May 2009. It scanned the microwave and submillimetre sky continuously between 12 August 2009 and 23 October 2013, producing deep, high-resolution, all-sky maps in nine frequency bands from 30 to 857GHz. This paper presents the cosmological legacy of Planck, which currently provides our strongest constraints on the parameters of the standard cosmological model and some of the tightest limits available on deviations from that model. The 6-parameter LCDM model continues to provide an excellent fit to the cosmic microwave background data at high and low redshift, describing the cosmological information in over a billion map pixels with just six parameters. With 18 peaks in the temperature and polarization angular power spectra constrained well, Planck measures five of the six parameters to better than 1% (simultaneously), with the best-determined parameter (theta_*) now known to 0.03%. We describe the multi-component sky as seen by Planck, the success of the LCDM model, and the connection to lower-redshift probes of structure formation. We also give a comprehensive summary of the major changes introduced in this 2018 release. The Planck data, alone and in combination with other probes, provide stringent constraints on our models of the early Universe and the large-scale structure within which all astrophysical objects form and evolve. We discuss some lessons learned from the Planck mission, and highlight areas ripe for further experimental advances.

[189] arXiv:1807.06188v1 [pdf, vox]

The SPIRIT Telescope Initiative: six years on

Paul Luckas
Submitted Tuesday 17 July 2018 @ 02:49:54 GMT
Published in the Proceedings for the 36th Annual Symposium on Telescope Science, 2017, 14 pages, 16 figures

Now in its sixth year of operation, the SPIRIT initiative remains unique in Australia, as a robust web-enabled robotic telescope initiative funded for education and outreach. With multiple modes of operation catering for a variety of usage scenarios and a fully supported education program, SPIRIT provides free access to contemporary astronomical tools for students and educators in Western Australia and beyond. The technical solution itself provides an excellent model for low cost robotic telescope installations, and the education program has evolved over time to include a broad range of student experiences - from engagement activities to authentic science. This paper details the robotic telescope solution, student interface and educational philosophy, summarises achievements and lessons learned and examines the possibilities for future enhancement including spectroscopy.

[190] arXiv:1807.04550v2 [pdf, vox]

Spectroscopic observation of planetary nebulae

Paul Luckas
Submitted Tuesday 17 July 2018 @ 02:09:27 GMT
Published in the Journal of the British Astronomical Association April, 2018. 6 pages, 9 figures

This paper describes how commercially available spectrographs can be used to identify and measure some basic characteristics of planetary nebulae.

[191] arXiv:1807.06177v1 [pdf, vox]

Identifying quasars with astrometric and mid-infrared methods from APOP and ALLWISE

Sufen Guo, Zhaoxiang Qi, Shilong Liao, Zihuang Cao, Mario G. Lattanzi, Beatrice Bucciarelli, Zhenghong Tang, Qing-Zeng Yan
Submitted Tuesday 17 July 2018 @ 01:54:29 GMT
7 pages, 7 figures, accepted by A&A

Context. Quasars are spatially stationary, and they are essential objects in astrometry when defining reference frames. However, the census of quasars is far from complete. Mid-infared colors can be used to find quasar candidates because AGNs show a peculiar appearance in mid-infrared color, but these methods are incapable of separating quasars from AGNs. Aims. The aim of our study is to use astrometric and mid-infrared methods to select quasars and get a reliable quasar candidates catalog. Methods. We used a near-zero proper motion criterion in conjuction with WISE (all-sky Wide-field Infrared Survey Explorer) [W1-W2] color to select quasar candidates. The [W1-W2] color criterion is defined by the linear boundary of two samples: LAMOST DR5 quasars, which serve as the quasar sample, and LAMOST DR5 stars and galaxies, which serve as the non-quasar sample. The contamination and completeness are evaluated. Results. We present a catalog of 662 753 quasar candidates, with a completeness of about 75% and a reliability of 77.2%.

[192] arXiv:1807.06155v1 [pdf, vox]

Statistical predictions for the first black holes

Tilman Hartwig
Submitted Tuesday 17 July 2018 @ 00:07:22 GMT
Preprint of the chapter "Statistical predictions for the first black holes", to be published in the review volume "Formation of the First Black Holes", Latif, M. and Schleicher, D. R. G., eds., World Scientific Publishing Company, 2018, pp 161-175 [see https://www.worldsci​entific.com/worldsci​books/10.1142/10652]​

The recent observations of supermassive black holes (SMBHs) at high redshift challenge our understanding of their formation and growth. There are different proposed pathways to form black hole (BH) seeds, such as the remnants of the first stars (chapter 4), gas-dynamical processes (chapter 5), direct collapse (chapter 6), or stellar collisions in dense nuclear clusters (chapter 7). In this chapter, we discuss the probability of forming supermassive black holes (SMBHs) via these channels and determine the expected number density of the BH seeds. We start with a brief discussion of the observational constraints on SMBHs at low and high redshift that theoretical models have to reproduce (a more detailed account is provided in chapter 12). We further present the most popular formation channels of SMBHs, discuss under which conditions they can reproduce the observations, and compare various estimates in the literature on the expected number density of SMBHs. To account for the density of quasars at $z>6$ requires very efficient gas accretion mechanisms or high BH seeds masses. The bottleneck to obtain sufficiently high number densities of seed BHs with masses $>10^5$M$_\odot$ is the interplay between radiative and chemical feedback, which constrains the conditions for primordial, isothermal gas collapse.

Submitted Mon, 16 Jul 2018

[193] arXiv:1807.06153v1 [pdf, vox]

Revisiting the iron abundance in the hyper iron-poor star HE$~$1327-2326 with UV COS/$HST$ data

Rana Ezzeddine, Anna Frebel
Submitted Monday 16 July 2018 @ 23:42:01 GMT
11 pages, 2 figures, 2 tables. Accepted for publication in ApJ

We present a new iron abundance analysis of the hyper metal-poor star HE$~$1327-2326, based on Fe II lines detected in its UV spectral range for the first time. In a Cosmic Origins Spectrograph (COS) spectrum, five new Fe II lines could be measured. A Si I line was also detected for the first time. We determine a 1D Local Thermodynamic Equilibrium (LTE) Fe II abundance of [Fe II/H] = -5.99$\pm$0.25. We also investigate departures from LTE for both Fe I and Fe II lines. Guided by 3D Non-LTE (NLTE) analyses of other well-studied metal-poor stars, we identify potential "residual" 3D effects in HE$~$1327-2326 arising from the absence of full 3D NLTE Fe calculations. Accordingly, we employ measurements of 10 weak Fe I lines previously detected in an optical spectrum of HE$~$1327-2326, as no Fe I lines are detectable in our UV spectrum. Following our previous work, we adopt the 1D NLTE Fe I abundance of [Fe/H] = -5.20$\pm$0.12 for HE$~$1327-2326. Adopting a value based on the optical Fe I rather than UV lines was heavily informed by our extensive investigation of model atmosphere and radiative transfer effects on different lines accross the entire UV-optical wavelength range. An iron abundance of [Fe/H] = -5.20$\pm$0.12 is only 0.2 dex higher than what was used in previous studies. Accordingly, no previous conclusions regarding the nature of the star are affected.

[194] arXiv:1807.06128v1 [pdf, vox]

Massively Parallel Simulations of Binary Black Hole Intermediate-Mass-Ra​tio Inspirals

Milinda Fernando, David Neilsen, Hyun Lim, Eric Hirschmann, Hari Sundar
Submitted Monday 16 July 2018 @ 21:54:42 GMT

We present a portable and highly-scalable algorithm and framework that targets problems in the astrophysics and numerical relativity communities. This framework combines together a parallel octree-refined adaptive mesh with wavelet adaptive multiresolution and a physics module to solve the Einstein equations of general relativity in the BSSN formulation. The goal of this work is to perform advanced, massively parallel numerical simulations of Intermediate Mass Ratio Inspirals (IMRIs) of binary black holes with mass ratios on the order of 100:1. These studies will be used to generate waveforms for use in LIGO data analysis and to calibrate semi-analytical approximate methods. This advanced framework is designed to easily accommodate many existing algorithms in astrophysics for plasma dynamics and radiation hydrodynamics. We have designed novel algorithms to enable efficient simulations for such experiments and demonstrate excellent weak scalability up to 131K cores on ORNL's Titan for binary mergers for mass ratios up to 100.

[195] arXiv:1807.06123v1 [pdf, vox]

Atmospheric Circulation and Thermal Phase-Curve Offset of Tidally and Non-Tidally Locked Terrestrial Exoplanets

James Penn, Geoffrey K Vallis
Submitted Monday 16 July 2018 @ 21:42:12 GMT

Using an idealised general circulation model, we investigate the atmospheric circulation of Earth-like terrestrial planets in a variety of orbital configurations. We relax the common assumption of the planet being tidally-locked, and look at the role atmospheric dynamics can have in the observed thermal phase curve when the substellar point is non-stationary. In slowly rotating planets, a moving forcing can induce strong jets in the upper troposphere, both prograde and retrograde, sensitive to the speed and direction of the diurnal forcing. We find that, consistent with previous shallow water model experiments, the thermal phase curve offset is sensitive to the velocity of the substellar point moving across the surface of the planet. For a planet with a known orbital period, the results show that the observed hotspot on the planet could be either east or west of the substellar point, depending on whether the planet is tidally-locked or not.

[196] arXiv:1807.06121v1 [pdf, vox]

Fast focal plane wavefront sensing on ground-based telescopes

Benjamin L. Gerard, Christian Marois, Raphaël Galicher, Jean-Pierre Véran
Submitted Monday 16 July 2018 @ 21:33:57 GMT

Exoplanet detection and characterization through extreme adaptive optics (ExAO) is a key science goal of future extremely large telescopes. This achievement, however, will be limited in sensitivity by both quasi-static wavefront errors and residual AO-corrected atmospheric wavefront errors. A solution to both of these problems is to use the science camera of an ExAO system as a wavefront sensor to perform a fast measurement and correction method to remove these aberrations as soon as they are detected. We have developed the framework for one such method, using the self-coherent camera (SCC), to be applied to ground-based telescopes, called Fast Atmospheric SCC Technique (FAST; Gerard et al., submitted). Our FAST solution requires an optimally designed coronagraph (the SCC FPM) and post-processing algorithm and is in principle able to reach a "raw" contrast of a few times the photon noise limit, continually improving with integration time. In this paper, we present new ongoing work in exploring the manufacturing limitations of the SCC FPM as well as a general framework to implement and optimize a FAST deformable mirror control loop.

[197] arXiv:1807.06116v1 [pdf, vox]

Moment-Based Ellipticity Measurement as a Statistical Parameter Estimation Problem

Nicolas Tessore, Sarah Bridle
Submitted Monday 16 July 2018 @ 21:21:16 GMT
10 pages, 7 figures; comments welcome, code available on request

We show that galaxy ellipticity estimation for weak gravitational lensing with unweighted image moments reduces to the problem of measuring a combination of the means of three independent normal random variables. Under very general assumptions, the intrinsic image moments of sources can be recovered from observations including effects such as the point-spread function and pixellation. Gaussian pixel noise turns these into three jointly normal random variables, the means of which are algebraically related to the ellipticity. We show that the random variables are approximately independent with known variances, and provide an algorithm for making them exactly independent. Once the framework is developed, we derive general properties of the ellipticity estimation problem, such as the signal-to-noise ratio, a generic form of an ellipticity estimator, and Cram\'er-Rao lower bounds for an unbiased estimator. We then derive the unbiased ellipticity estimator using unweighted image moments. We find that this unbiased estimator has a poorly behaved distribution and does not converge in practical applications, but demonstrates how to derive and understand the behaviour of new moment-based ellipticity estimators.

[198] arXiv:1807.06115v1 [pdf, vox]

The Orbit of the Close Companion of Polaris: Hubble Space Telescope Imaging 2007 to 2014

Nancy Remage Evans, Margarita Karovska, Howard E. Bond, Gail H. Schaefer, Kailash C. Sahu, Jennifer Mack, Edmund P. Nelan, Alexandre Gallenne, Evan D. Tingle
Submitted Monday 16 July 2018 @ 21:14:27 GMT
Accepted by Astrophysical Journal

As part of a program to determine dynamical masses of Cepheids, we have imaged the nearest and brightest Cepheid, Polaris, with the Hubble Space Telescope Wide Field Planetary Camera 2 and Wide Field Camera 3. Observations were obtained at three epochs between 2007 and 2014. In these images, as in HST frames obtained in 2005 and 2006, which we discussed in a 2008 paper, we resolve the close companion Polaris Ab from the Cepheid Polaris Aa. Because of the small separation and large magnitude difference between Polaris Aa and Ab, we used PSF deconvolution techniques to carry out astrometry of the binary. Based on these new measurements, we have updated the elements for the 29.59 yr orbit. Adopting the distance to the system from the recent Gaia Data Release 2, we find a dynamical mass for the Cepheid of 3.45 +/- 0.75 Msun, although this is preliminary, and will be improved by CHARA measurements covering periastron. As is the case for the recently determined dynamical mass for the Cepheid V1334 Cyg, the mass of Polaris is significantly lower than the "evolutionary mass" predicted by fitting to evolutionary tracks in the HR diagram. We discuss several questions and implications raised by these measurements, including the pulsation mode, which instability-strip crossing the stars are in, and possible complications such as rotation, mass loss, and binary mergers. The distant third star in the system, Polaris B, appears to be older than the Cepheid, based on isochrone fitting. This may indicate that the Cepheid Polaris is relatively old and is the result of a binary merger, rather than being a young single star.

[199] arXiv:1807.06102v1 [pdf, vox]

What Does "Metallicity" Mean When Interpreting Spectra of Exoplanetary Atmospheres?

Kevin Heng
Submitted Monday 16 July 2018 @ 20:48:49 GMT
Accepted by RNAAS. 3 pages, 1 figure

One of the desired outcomes of studying exoplanetary atmospheres is to set decisive constraints on exoplanet formation theories. Astronomers often speak of the "metallicity" in broad terms. When modeling the bulk metallicity, workers refer to the elemental iron abundance (Fe/H). By contrast, when exo-atmospheric astronomers speak of the "metallicity" derived from analysing low-resolution Hubble and Spitzer spectrophotometry, they are referring to the elemental abundances of oxygen (O/H), carbon (C/H) and nitrogen (N/H): in decreasing order of importance, since spectra from the Hubble Wide Field Camera 3 are primarily sensitive to water with secondary contributions from hydrogen cyanide and ammonia, while Spitzer photometry is sensitive to methane and carbon monoxide. From retrieving for the water abundances, workers such as Kreidberg et al. (2014), Wakeford et al. (2017, 2018), Arcangeli et al. (2018) and Mansfield et al. (2018) have published figures that show the "metallicity" versus the masses of the exoplanets. Even if we assume that bulk and atmospheric elemental abundances are equal, the motivation behind this research note is to demonstrate that the conversion between the water abundance and O/H is not straightforward. "Water at solar metallicity" is a temperature- and pressure-dependent statement, because there is no single value of the water volume mixing ratio corresponding to solar values of O/H and C/H. Overall, the conversion factor between the water volume mixing ratio and O/H is not unity and depends on temperature, pressure, O/H, C/H and C/O, even without invoking disequilibrium chemistry (photochemistry and/or atmospheric mixing). It remains unproven that disequilibrium chemistry or condensation will always return a conversion factor of unity. It is thus a fair statement to say that the "metallicity" estimates inferred from atmospheric retrievals are model-dependent.

[200] arXiv:1807.06095v1 [pdf, vox]

Nonlinear librations of distant retrograde orbits: a perturbative approach -- The Hill problem case

Martin Lara
Submitted Monday 16 July 2018 @ 20:26:53 GMT
42 pages, 16 figures

The non-integrability of the Hill problem makes that its global dynamics must be necessarily approached numerically. However, the analytical approach is feasible in the computation of relevant solutions. In particular, the nonlinear dynamics of the Hill problem close to the origin, and the libration point dynamics have been thoroughly investigated by perturbation methods. Out of the Hill sphere, the analytical approach is also feasible, at least in the case of distant retrograde orbits. Previous analytical investigations of this last case succeeded in the qualitative description of the dynamics, but they commonly failed in providing accurate results. This is a consequence of the essential dependance of the dynamics on elliptic functions, a fact that makes to progress in the perturbation approach beyond the lower orders of the solution really difficult. We propose an alternative perturbation approach that allows us to provide a very simple low order analytical solution in trigonometric functions, on the one hand, and, while still depending on special functions, to compute higher orders of the solution, on the other.

[201] arXiv:1807.06092v1 [pdf, vox]

The Athena X-ray Integral Field Unit

Didier Barret, Thien Lam Trong, Jan-Willem den Herder, Luigi Piro, Massimo Cappi, Juhani Huovelin, Richard Kelley, J. Miguel Mas-Hesse, Kazuhisa Mitsuda, Stéphane Paltani, Gregor Rauw, Agata Rozanska, Joern Wilms, Simon Bandler, Marco Barbera, Xavier Barcons, Enrico Bozzo, Maria Teresa Ceballos, Ivan Charles, Elisa Costantini, Anne Decourchelle, Roland den Hartog, Lionel Duband, Jean-Marc Duval, Fabrizio Fiore, Flavio Gatti, Andrea Goldwurm, Brian Jackson, Peter Jonker, Caroline Kilbourne, Claudio Macculi, Mariano Mendez, Silvano Molendi, Piotr Orleanski, François Pajot, Etienne Pointecouteau, Frederick Porter, Gabriel W. Pratt, Damien Prêle, Laurent Ravera, Kosuke Sato, Joop Schaye, Keisuke Shinozaki, Tanguy Thibert, Luca Valenziano, Veronique Valette, Jacco Vink, Natalie Webb, Michael Wise, Noriko Yamasaki, Françoise Delcelier-Douchin, Jean-Michel Mesnager, Bernard Pontet, Alice Pradines, Graziella Branduardi-Raymont, Esra Bulbul, Mauro Dadina, Stefano Ettori, Alexis Finoguenov, Yasushi Fukazawa, Agnieszka Janiuk, Jelle Kaastra, Pasquale Mazzotta, Jon Miller, Giovanni Miniutti, Yaël Nazé, Fabrizio Nicastro, Salvatore Sciortino, Aurora Simionescu, Jose Miguel Torrejon, Benoît Frezouls, Hervé Geoffray, Philippe Peille, Corinne Aicardi, Jérôme André, Antoine Clénet, Christophe Daniel, Christophe Etcheverry, Emilie Gloaguen, Gilles Hervet, Antoine Jolly, Aurélien Ledot, Irwin Maussang, Alexis Paillet, Roseline Schmisser, Bruno Vella, Jean-Charles Damery, Kevin Boyce, Michael DiPirro, Simone Lotti, Denis Schwander, Stephen Smith, Bert-Joost van Leeuwen, Henk van Weers, Nicolas Clerc, Beatriz Cobo, Thomas Dauser, Jelle de Plaa, Christian Kirsch, Edoardo Cucchetti, Megan Eckart, Philippe Ferrando, Lorenzo Natalucci
Submitted Monday 16 July 2018 @ 20:22:40 GMT
15 pages, 5 figures, to appear in Proc. SPIE Astronomical Telescopes and Instrumentation, Austin 2018

The X-ray Integral Field Unit (X-IFU) is the high resolution X-ray spectrometer of the ESA Athena X-ray observatory. Over a field of view of 5' equivalent diameter, it will deliver X-ray spectra from 0.2 to 12 keV with a spectral resolution of 2.5 eV up to 7 keV on ~5 arcsecond pixels. The X-IFU is based on a large format array of super-conducting molybdenum-gold Transition Edge Sensors cooled at about 90 mK, each coupled with an absorber made of gold and bismuth with a pitch of 249 microns. A cryogenic anti-coincidence detector located underneath the prime TES array enables the non X-ray background to be reduced. A bath temperature of about 50 mK is obtained by a series of mechanical coolers combining 15K Pulse Tubes, 4K and 2K Joule-Thomson coolers which pre-cool a sub Kelvin cooler made of a 3He sorption cooler coupled with an Adiabatic Demagnetization Refrigerator. Frequency domain multiplexing enables to read out 40 pixels in one single channel. A photon interacting with an absorber leads to a current pulse, amplified by the readout electronics and whose shape is reconstructed on board to recover its energy with high accuracy. The defocusing capability offered by the Athena movable mirror assembly enables the X-IFU to observe the brightest X-ray sources of the sky (up to Crab-like intensities) by spreading the telescope point spread function over hundreds of pixels. Thus the X-IFU delivers low pile-up, high throughput (>50%), and typically 10 eV spectral resolution at 1 Crab intensities, i.e. a factor of 10 or more better than Silicon based X-ray detectors. In this paper, the current X-IFU baseline is presented, together with an assessment of its anticipated performance in terms of spectral resolution, background, and count rate capability. The X-IFU baseline configuration will be subject to a preliminary requirement review that is scheduled at the end of 2018.

[202] arXiv:1807.06088v1 [pdf, vox]

Exoplanet science with a space-based mid-infrared nulling interferometer

Sascha P. Quanz, Jens Kammerer, Denis Defrère, Olivier Absil, Adrian M. Glauser, Daniel Kitzmann
Submitted Monday 16 July 2018 @ 20:14:37 GMT
17 pages (incl. 7 figures); Proc. SPIE Astronomical Telescopes + Instrumentation 2018 (Austin; Texas), Optical and Infrared Interferometry and Imaging VI

One of the long-term goals of exoplanet science is the (atmospheric) characterization of a large sample (>100) of terrestrial planets to assess their potential habitability and overall diversity. Hence, it is crucial to quantitatively evaluate and compare the scientific return of various mission concepts. Here we discuss the exoplanet yield of a space-based mid-infrared (MIR) nulling interferometer. We use Monte-Carlo simulations, based on the observed planet population statistics from the Kepler mission, to quantify the number and properties of detectable exoplanets (incl. potentially habitable planets) and we compare the results to those for a large aperture optical/NIR space telescope. We investigate how changes in the underlying technical assumptions (sensitivity and spatial resolution) impact the results and discuss scientific aspects that influence the choice for the wavelength coverage and spectral resolution. Finally, we discuss the advantages of detecting exoplanets at MIR wavelengths, summarize the current status of some key technologies, and describe what is needed in terms of further technology development to pave the road for a space-based MIR nulling interferometer for exoplanet science.

[203] arXiv:1807.06085v1 [pdf, vox]

Evolution of galaxy size--stellar mass relation from the Kilo Degree Survey

N. Roy, N. R. Napolitano, F. La Barbera, C. Tortora, F. Getman, M. Radovich, M. Capaccioli, M. Brescia, S. Cavuoti, G. Longo, M. A. Raj, E. Puddu, G. Covone, V. Amaro, C. Vellucci, A. Grado, K. Kuijken, G. Verdoes Kleijn, E. Valentijn
Submitted Monday 16 July 2018 @ 20:01:08 GMT
accepted by MNRAS

We have obtained structural parameters of about 340,000 galaxies from the Kilo Degree Survey (KiDS) in 153 square degrees of data release 1, 2 and 3. We have performed a seeing convolved 2D single S\'ersic fit to the galaxy images in the 4 photometric bands (u, g, r, i) observed by KiDS, by selecting high signal-to-noise ratio (S/N > 50) systems in every bands. We have classified galaxies as spheroids and disc-dominated by combining their spectral energy distribution properties and their S\'ersic index. Using photometric redshifts derived from a machine learning technique, we have determined the evolution of the effective radius, \Re\ and stellar mass, \mst, versus redshift, for both mass complete samples of spheroids and disc-dominated galaxies up to z ~ 0.6. Our results show a significant evolution of the structural quantities at intermediate redshift for the massive spheroids ($\mbox{Log}\ M_*/M_\odot>11$, Chabrier IMF), while almost no evolution has found for less massive ones ($\mbox{Log}\ M_*/M_\odot < 11$). On the other hand, disc dominated systems show a milder evolution in the less massive systems ($\mbox{Log}\ M_*/M_\odot < 11$) and possibly no evolution of the more massive systems. These trends are generally consistent with predictions from hydrodynamical simulations and independent datasets out to redshift z ~ 0.6, although in some cases the scatter of the data is large to drive final conclusions. These results, based on 1/10 of the expected KiDS area, reinforce precedent finding based on smaller statistical samples and show the route toward more accurate results, expected with the the next survey releases.

[204] arXiv:1807.06080v1 [pdf, vox]

Growth and Feedback from the First Black Holes

John H. Wise
Submitted Monday 16 July 2018 @ 19:55:34 GMT
30 pages, 6 figures. Preprint of a review volume chapter to be published in Latif, M., & Schleicher, D.R.G., "Growth and Feedback from the First Black Holes'', Formation of the First Black Holes, 2018. Copyright World Scientific Publishing Company, https://www.worldsci​entific.com/worldsci​books/10.1142/10652

Regardless of their initial seed mass, any active galactic nuclei observed at redshifts z > 6 must have grown by several orders of magnitude from their seeds. In this chapter, we will discuss the physical processes and latest research on black hole growth and associated feedback after seed formation. Fueling is initially slowed down by radiative feedback from the black hole itself and supernova explosions from nearby stars. Its growth however accelerates once the host galaxy grows past a critical mass.

[205] arXiv:1807.06079v1 [pdf, vox]

Gamma-ray emission of hot astrophysical plasma

Ervin Kafexhiu, Felix Aharonian, Maxim Barkov
Submitted Monday 16 July 2018 @ 19:55:21 GMT
11 pages, 10 figures

Very hot plasmas with ion temperature exceeding $10^{10}$~K can be formed in certain astrophysical environments. The distinct radiation signature of such plasmas is the $\gamma$-ray emission dominated by the prompt de-excitation nuclear lines and $\pi^0$-decay $\gamma$-rays. Using a large nuclear reaction network, we compute the time evolution of the chemical composition of such hot plasmas and their $\gamma$-ray line emissivity. At higher energies, we provide simple but accurate analytical presentations for the $\pi^0$-meson production rate and the corresponding $\pi^0\to2\gamma$ emissivity derived for the Maxwellian distribution of protons. We discuss the impact of the possible deviation of the high energy tail of the particle distribution function from the "nominal" Maxwellian distribution on the plasma $\gamma$-ray emissivity.

[206] arXiv:1807.06066v1 [pdf, vox]

SDSS-IV MaNGA: Spatially resolved star-formation histories and the connection to galaxy physical properties

K. Rowlands, T. Heckman, V. Wild, N. L. Zakamska, V. Rodriguez-Gomez, J. Barrera-Ballesteros, J. Lotz, D. Thilker, B. H. Andrews, J. Brinkmann, M. Boquien, J. R. Brownstein, H-C. Hwang, R. Smethurst
Submitted Monday 16 July 2018 @ 19:18:26 GMT
Accepted for publication in MNRAS. 16 pages, 14 figures

A key task of observational extragalactic astronomy is to determine where -- within galaxies of diverse masses and morphologies -- stellar mass growth occurs, how it depends on galaxy properties and what processes regulate star formation. Using spectroscopic indices derived from the stellar continuum at $\sim 4000$\AA, we determine the spatially resolved star-formation histories of 980000 spaxels in 2404 galaxies in the SDSS-IV MaNGA IFU survey. We examine the spatial distribution of star-forming, quiescent, green valley, starburst and post-starburst spaxels as a function of stellar mass and morphology to see where and in what types of galaxy star formation is occurring. The spatial distribution of star-formation is dependent primarily on stellar mass, with a noticeable change in the distribution at \mstar$>10^{10}$\msu​n. Galaxies above this mass have an increasing fraction of regions that are forming stars with increasing radius, whereas lower mass galaxies have a constant fraction of star forming regions with radius. Our findings support a picture of inside-out growth and quenching at high masses. We find that morphology (measured via concentration) correlates with the fraction of star-forming spaxels, but not with their radial distribution. We find (post-)starburst regions are more common outside of the galaxy centre, are preferentially found in asymmetric galaxies, and have lower gas-phase metallicity than other regions, consistent with interactions triggering starbursts and driving low metallicity gas into regions at $<1.5R_e$.

[207] arXiv:1807.06059v1 [pdf, vox]

The Pulsar Search Collaboratory: Expanding Nationwide

Kathryn Williamson, Maura McLaughlin, Sue Ann Heatherly, John Stewart, Duncan Lorimer, Harsha Blumer, Cabot Zabriskie, Ryan Lynch
Submitted Monday 16 July 2018 @ 18:52:45 GMT
6 pages, 1 figure, accepted for publication in The Physics Teacher

The Pulsar Search Collaboratory (PSC) engages high school students and teachers in analyzing real data from the Robert C. Byrd Green Bank Telescope for the purpose of discovering exotic stars called pulsars. These cosmic clocks can be used as a galactic-scale detector of gravitational waves, ripples in space-time that have recently been directly detected from the mergers of stellar-mass black holes. Through immersing students in an authentic, positive learning environment to build a sense of belonging and competency, the goal of the PSC is to promote students' long-term interests in science and science careers. PSC students have discovered 7 pulsars since the start of the PSC in 2008. Originally targeted at teachers and students in West Virginia, over time the program has grown to 18 states. In a new effort to scale the PSC nationally, the PSC has developed an integrated online training program with both self-guided lectures and homework and real-time interactions with pulsar astronomers. Now, any high school student can join in the exciting search for pulsars and the discovery of a new type of gravitational waves.

[208] arXiv:1807.06055v1 [pdf, vox]

Formation of the First Black Holes: Current observational status

Dominik R. G. Schleicher
Submitted Monday 16 July 2018 @ 18:44:30 GMT
Preprint of the chapter "Current Observational Status", to be published in the review volume "Formation of the First Black Holes", Latif, M. and Schleicher, D.R.G., eds., World Scientific Publishing Company, 2018, pp 223-238 [see https://www.worldsci​entific.com/worldsci​books/10.1142/10652]​

In this chapter, we review the current observational status of the first supermassive black holes. It is clear that such a review can hardly be complete, due to the wealth of surveys that has been pursued, including different wavelengths and different observational techniques. This chapter will focus on the main results that have been obtained, considering the detections of z~6 supermassive black holes in large surveys such as SDSS, CFHQS and Pan-STARRS. In addition, we will discuss upper limits and constraints on the population of the first black holes that can be derived from observational data, in particular in the X-ray regime, as these provide additional relevant information for the comparison with formation scenarios.

[209] arXiv:1807.06049v1 [pdf, vox]

A collection of model stellar spectra for spectral types B to early-M

Carlos Allende Prieto, Lars Koesterke, Ivan Hubeny, Manuel A. Bautista, Paul S. Barklem, Sultana N. Nahar
Submitted Monday 16 July 2018 @ 18:29:42 GMT
7 pages, 4 figures. To appear in A&A

Models of stellar spectra are necessary for interpreting light from individual stars, planets, integrated stellar populations, nebulae, and the interstellar medium. We provide a comprehensive and homogeneous collection of synthetic spectra for a wide range of atmospheric parameters and chemical compositions. We compile atomic and molecular data from the literature. We adopt the largest and most recent set of ATLAS9 model atmospheres, and use the radiative code ASS$\epsilon$T.The resulting collection of spectra is made publicly available at medium and high-resolution ($R\equiv\lambda/\de​lta\lambda$ = 10,000, 100,000 and 300,000 spectral grids, which include variations in effective temperature between 3500 K and 30,000 K, surface gravity ($0\le \log g \le 5$), and metallicity ($-5 \le$[Fe/H]$\le +0. 5$), spanning the wavelength interval 120-6500 nm. A second set of denser grids with additional dimensions, [$\alpha$/Fe] and micro-turbulence, are also provided (covering 200-2500 nm). We compare models with observations for a few representative cases.

[210] arXiv:1807.06048v1 [pdf, vox]

Vector disformal transformation of generalized Proca theory

Guillem Domènech, Shinji Mukohyama, Ryo Namba, Vassilis Papadopoulos
Submitted Monday 16 July 2018 @ 18:25:15 GMT

Motivated by the GW170817/GRB170817A constraint on the deviation of the speed of gravitational waves from that of photons, we study disformal transformations of the metric in the context of the generalized Proca theory. The constraint restricts the form of the gravity Lagrangian, the way the electromagnetism couples to the gravity sector on cosmological backgrounds, or in general a combination of both. Since different ways of coupling matter to gravity are typically related to each other by disformal transformations, it is important to understand how the structure of the generalized Proca Lagrangian changes under disformal transformations. For disformal transformations with constant coefficients we provide the complete transformation rule of the Lagrangian. We find that additional terms, which were considered as beyond generalized Proca in the literature, are generated by the transformations. Once these additional terms are included, on the other hand, the structure of the gravity Lagrangian is preserved under the transformations. We then derive the transformation rules for the sound speeds of the scalar, vector and tensor perturbations on a homogeneous and isotropic background. We explicitly show that they transform following the natural expectation of metric transformations, that is, according to the transformation of the background lightcone structure. We end by arguing that inhomogeneities due to structures in the universe, e.g. dark matter halos, generically changes the speed of gravitational waves from its cosmological value. We give a rough estimate of the effect of inhomogeneities and find that the fine-tuning should not depend on the background or that the fine-tuned theory has to be further fine-tuned to pass the tight constraint.

[211] arXiv:1807.06047v1 [pdf, vox]

The scalar spectra of primordial perturbations in loop quantum cosmology

Aurélien Barrau, Pierre Jamet, Killian Martineau, Flora Moulin
Submitted Monday 16 July 2018 @ 18:20:40 GMT

This article is devoted to the study of scalar perturbations in loop quantum cosmology. It aims at clarifying the situation with respect to the way initial conditions are set and to the specific choice of an inflaton potential. Several monomial potentials are studied. Both the dressed metric and deformed algebra approaches are considered. We show that the calculation of the ultra-violet part of the spectrum, which is the physically relevant region for most background trajectories, is reliable whereas the infra-red and intermediate parts do depend on some specific choices that are made explicit.

[212] arXiv:1807.06033v1 [pdf, vox]

Metallicity-Dependen​t Signatures in the Kepler Planets

James E. Owen, Ruth Murray-Clay
Submitted Monday 16 July 2018 @ 18:02:00 GMT
To appear in MNRAS

Using data from the California-Kepler-Su​rvey (CKS) we study trends in planetary properties with host star metallicity for close-in planets. By incorporating knowledge of the properties of the planetary radius gap identified by the CKS survey, we are able to investigate the properties of planetary cores and their gaseous envelopes separately. Our primary findings are that the solid core masses of planets are higher around higher metallicity stars and that these more massive cores were able to accrete larger gas envelopes. Furthermore, investigating the recently reported result that planets with radii in the range (2-6Rearth) are more common at short periods around higher metallicity stars in detail, we find that the average host star metallicity of H/He atmosphere-hosting planets increases smoothly inside an orbital period of ~20 days. We interpret the location of the metallicity increase within the context of atmospheric photoevaporation: higher metallicity stars are likely to host planets with higher atmospheric metallicity, which increases the cooling in the photoevaporative outflow, lowering the mass-loss rates. Therefore, planets with higher metallicity atmospheres are able to resist photoevaporation at shorter orbital periods. Finally, we find evidence at 2.8 sigma that planets that do not host H/He atmospheres at long periods are more commonly found around lower metallicity stars. Such planets are difficult to explain by photoevaporative stripping of planets which originally accreted H/He atmospheres. Alternatively, this population of planets could be representative of planets that formed in a terrestrial-like fashion, after the gas disc dispersed.

[213] arXiv:1807.06025v1 [pdf, vox]

The Distance of the Dark Matter Deficient Galaxy NGC1052-DF2

Pieter van Dokkum, Shany Danieli, Yotam Cohen, Charlie Conroy
Submitted Monday 16 July 2018 @ 18:00:03 GMT
Submitted to ApJ Letters. The key point of the paper is made in Figure 2. The ArtPop model images for NGC1052-DF2, the DOLPHOT catalogs, and the HST data for all galaxies are available upon request

We recently inferred that the galaxy NGC1052-DF2 has little or no dark matter and a rich system of unusual globular clusters. We assumed that the galaxy is a satellite of the luminous elliptical galaxy NGC1052 at ~20 Mpc, on the basis of its surface brightness fluctuations (SBF) distance of $19.0 \pm 1.7$ Mpc, its radial velocity of ~1800 km/s, and its projected position. Trujillo et al. (2018) proposed a much closer distance of 13 Mpc, based largely on a putative detection of the tip of the red giant branch (TRGB) in the color-magnitude diagram (CMD) and a recalibration of our SBF measurement. Here we analyze the CMD using both fully populated galaxy models and other galaxies in our HST sample, and demonstrate that Trujillo et al. almost certainly confused blends for individual red giants in their analysis. These blends produce a "phantom" TRGB ~2 times brighter than the true TRGB, leading to a ~1.4 times smaller inferred distance. The large population of unblended stars on the red giant branch expected for distances of ~13 Mpc is not detected in the HST data. We also provide a new distance measurement to NGC1052-DF2 that is free of calibration uncertainties, by anchoring it to a satellite of the megamaser host galaxy NGC4258. From a megamaser-TRGB-SBF distance ladder we obtain $D=18.7 \pm 1.7$ Mpc, consistent with our previous measurement and with the distance to NGC1052.

[214] arXiv:1807.06022v1 [pdf, vox]

The hyperluminous Compton-thick $z\sim2$ quasar nucleus of the hot DOG W1835+4355 observed by NuSTAR

L. Zappacosta, E. Piconcelli, F. Duras, C. Vignali, R. Valiante, S. Bianchi, A. Bongiorno, F. Fiore, C. Feruglio, G. Lanzuisi, R. Maiolino, S. Mathur, G. Miniutti, C. Ricci
Submitted Monday 16 July 2018 @ 18:00:02 GMT
11 pages, 5 figures, accepted for publication in Astronomy & Astrophysics, Main Journal

We present a 155ks NuSTAR observation of the $z\sim2$ hot dust-obscured galaxy (hot DOG) W1835+4355. We extracted spectra from the two NuSTAR detectors and analyzed them jointly with the archival XMM PN and MOS spectra. We performed a spectroscopic analysis based on both phenomenological and physically motivated models employing toroidal and spherical geometry for the obscurer. In all the modelings, the source exhibits a Compton-thick column density $N_{\rm H} \gtrsim 10^{24}$ cm$^{-2}$, a 2-10 keV luminosity $L_{2-10}\approx2\ti​mes10^{45}$ erg s$^{-1}$ , and a prominent soft excess ($\sim5-10$ % of the primary radiative output), which translates into a luminosity $\sim10^{44}$ erg s$^{-1}$. We modeled the spectral energy distribution from 1.6 to 850 $\mu m$ using a clumpy two-phase dusty torus model plus a modified blackbody to account for emission powered by star formation in the far-infrared. We employed several geometrical configurations consistent with those applied in the X-ray analysis. In all cases we obtained a bolometric luminosity $L_{\rm bol}\approx3-5\times​10^{47}$ erg s$^{-1}$, which confirms the hyperluminous nature of this active galactic nucleus. Finally, we estimate a prodigious star formation rate of $\sim$3000 $M_{\odot}\,yr^{-1}$​, which is consistent with the rates inferred for $z\approx2-4$ hyperluminous type I quasars. The heavily obscured nature, together with $L_{\rm bol}$, the ratio of X-ray to mid-infrared luminosity, the rest-frame optical morphology, and the host star formation rate are indicative of its evolutionary stage. We can interpret this as a late-stage merger event in the transitional, dust-enshrouded, evolutionary phase eventually leading to an optically bright AGN.

[215] arXiv:1807.06024v1 [pdf, vox]

Search for Extra-Galactic Intelligence Signal Synchronized with a Binary Neutron Star Merger

Yuki Nishino, Naoki Seto
Submitted Monday 16 July 2018 @ 18:00:02 GMT
6 pages, 1 figure, Accepted for publication in ApJL

We discuss the possibility of receiving a radio signal from extra-Galactic intelligence, around the time when we observe a binary neutron star merger in their galaxy. High precession measurements of the binary parameters allow them to send the signal ~ $10^4$ years before they themselves observe the merger signal. Using the SKA, we might receive ~ $10^4$ bits of data, transmitted from 40Mpc distance with the output power of ~ 1 TW. We also discuss related topics for GW170817 and mention potential roles of future gravitational wave detectors in relation to this transmission scheme.

[216] arXiv:1807.06018v1 [pdf, vox]

Scalar Field Dark Matter: Helping or Hurting Small-Scale Problems in Cosmology?

Victor H. Robles, James S. Bullock, Michael Boylan-Kolchin
Submitted Monday 16 July 2018 @ 18:00:01 GMT
13 pages, 8 figures, submitted to MNRAS

Building upon results of cosmological simulations of ultra-light scalar field dark matter (SFDM), we present a comprehensive model for the density profiles of SFDM haloes as a function of halo virial mass $M_{\rm h}$ and scalar field mass $m$. The central regions of SFDM haloes are dominated by solitons with characteristic densities that increase with increasing halo mass and asymptote to CDM-like profiles at large radii. For scalar field masses $m \sim 10^{-22}$ eV, consistent with large-scale structure observations, $M_{\rm h} \sim 10^{10} \,M_\odot$ haloes have lower core densities than their Cold Dark Matter (CDM) counterparts and this alleviates the Too Big to Fail problem (TBTF) in a regime where feedback is less effective. However, higher-mass SFDM haloes with $M_{\rm h} \sim 10^{11} \,M_\odot$ are denser than their CDM counterparts at small, observationally relevant radii. We use rotation curves of $V \sim 100$ km s$^{-1}$ galaxies from the SPARC database to show that SFDM exacerbates the cusp/core and central density problems seen in CDM at this scale. We conclude that if the conventional cosmological SFDM scaling relations are correct, then baryonic feedback is required to lower densities in SFDM haloes even more so than in CDM. This motivates cosmological and self-consistent hydrodynamic simulations of SFDM to determine whether central soliton structure can be altered by realistic feedback implementations.

[217] arXiv:1807.06019v1 [pdf, vox]

Optimizing the Efficiency of Fabry-Perot Interferometers with Silicon-Substrate Mirrors

Nicholas F. Cothard, Mahiro Abe, Thomas Nikola, Gordon J. Stacey, German Cortes-Medellin, Patricio A. Gallardo, Brian J. Koopman, Michael D. Niemack, Stephen C. Parshley, Eve M. Vavagiakis, Kenneth J. Vetter
Submitted Monday 16 July 2018 @ 18:00:01 GMT
Presented at SPIE Advances in Optical and Mechanical Technologies for Telescopes and Instrumentation III, June 14, 2018

We present the novel design of microfabricated, silicon-substrate based mirrors for use in cryogenic Fabry-Perot Interferometers (FPIs) for the mid-IR to sub-mm/mm wavelength regime. One side of the silicon substrate will have a double-layer metamaterial anti-reflection coating (ARC) anisotropically etched into it and the other side will be metalized with a reflective mesh pattern. The double-layer ARC ensures a reflectance of less than 1% at the surface substrate over the FPI bandwidth. This low reflectance is required to achieve broadband capability and to mitigate contaminating resonances from the silicon surface. Two silicon substrates with their metalized surfaces facing each other and held parallel with an adjustable separation will compose the FPI. To create an FPI with nearly uniform finesse over the FPI bandwidth, we use a combination of inductive and capacitive gold meshes evaporated onto the silicon substrate. We also consider the use of niobium as a superconducting reflective mesh for long wavelengths to eliminate ohmic losses at each reflection in the resonating cavity of the FPI and thereby increase overall transmission. We develop these silicon-substrate based FPIs for use in ground (e.g. CCAT-prime), air (e.g. HIRMES), and future space-based telescopes (e.g. the Origins Space Telescope concept). Such FPIs are well suited for spectroscopic imaging with the upcoming large IR/sub-mm/mm TES bolometer detector arrays. Here we present the fabrication and performance of multi-layer, plasma-etched, silicon metamaterial ARC, as well as models of the mirrors and FPIs.

[218] arXiv:1807.06021v1 [pdf, vox]

Forecasts on dark energy from the X-ray cluster survey with eROSITA: constraints from counts and clustering

Annalisa Pillepich, Thomas H. Reiprich, Cristiano Porciani, Katharina Borm, Andrea Merloni
Submitted Monday 16 July 2018 @ 18:00:01 GMT
Submitted to MNRAS. Main results at Figure 2 and Table 5

We forecast the potential of the forthcoming X-ray galaxy-cluster survey with eROSITA to constrain dark-energy models. We focus on spatially-flat cosmological scenarios with either constant or time-dependent dark-energy equation-of-state parameters. Fisher information is extracted from the number density and spatial clustering of a photon-count-limited sample of clusters of galaxies up to z~2. We consider different scenarios for the availability of (i) X-ray follow-up observations, (ii) photometric and spectroscopic redshifts, and (iii) accurate knowledge of the observable -- mass relation down to the scale of galaxy groups. With about 125,000 clusters (detected with more than 50 photons and with mass M500c > $10^{13} h^{-1}$ Msun) from an average all-sky exposure of 1.6 ks, eROSITA will give marginalized, one-dimensional, 1-$\sigma$ errors of $\Delta \sigma_8 = \pm~0.008$ ($\sim$1 per cent), $\Delta \Omega_{\rm M} = \pm~0.006$ (2.2 per cent), $\Delta w_0 = \pm~0.07$ (7 per cent), and $\Delta w_a = \pm~0.25$ (optimistic scenario) in combination with (and largely improving upon) current constraints from various cosmological probes (cosmic microwave background, BAOs, Type Ia SNe). Our findings correspond to a dark-energy figure of merit in the range of $116-162$ (after the four years of all-sky survey), making eROSITA one of the first Stage IV experiments to come on line according to the classification of the Dark Energy Task Force. To secure improved mass calibrations and to include high-redshift clusters (z > 0.5) as well as objects at the group-mass scale (M500c < 5 $\times~ 10^{13} h^{-1}$ Msun) will be vital to reach such accuracies.

[219] arXiv:1807.06011v1 [pdf, vox]

Imprints of white dwarf recoil in the separation distribution of Gaia wide binaries

Kareem El-Badry, Hans-Walter Rix
Submitted Monday 16 July 2018 @ 18:00:00 GMT
14 pages, 10 figures, plus appendices. Submitted to MNRAS. Catalog available at https://sites.google​.com/site/dr2binarie​s200pc/data

We construct from Gaia DR2 an extensive and very pure ($\lesssim 0.2\%$ contamination) catalog of wide binaries containing main-sequence (MS) and white dwarf (WD) components within 200 fpc of the Sun. The public catalog contains, after removal of clusters and higher-order multiples, $>$50,000 MS/MS, $>$3,000 WD/MS, and nearly 400 WD/WD binaries with projected separations of $50 \lesssim s/{\rm AU} < 50,000$. Accounting for incompleteness and selection effects, we model the separation distribution of each class of binaries as a broken power-law, revealing marked differences between the three populations. The separation distribution of MS/MS systems is nearly consistent with a single power-law of slope $-1.6$ over at least $500 < s/{\rm AU} < 50,000$, with marginal steepening at $s > 10,000$ AU. In contrast, the separation distributions of WD/MS and WD/WD binaries show distinct breaks at $\sim$ 3,000 AU and $\sim$1,500 AU, respectively: they are flatter than the MS/MS distribution at small separations and steeper at large separations. Using binary population synthesis models, we show that these breaks are unlikely to be caused by external factors but can be explained if the WDs incur a kick of $\sim$ 0.75 km s$^{-1}$ during their formation, presumably due to asymmetric mass loss. The data rule out typical kick velocities above 2km s$^{-1}$. Our results imply that most wide binaries with separations exceeding a few thousand AU become unbound during post-MS evolution.

[220] arXiv:1807.06012v1 [pdf, vox]

The TRENDS High-Contrast Imaging Survey. VII. Discovery of a Nearby Sirius-like White Dwarf System (HD 169889)

Justin R. Crepp, Erica J. Gonzales, Brendan P. Bowler, Farisa Morales, Jordan Stone, Eckhart Spalding, Amali Vaz, Philip Hinz, Steve Ertel, Andrew Howard, Howard Isaacson
Submitted Monday 16 July 2018 @ 18:00:00 GMT
Accepted to ApJ

Monitoring the long-term radial velocity (RV) and acceleration of nearby stars has proven an effective method for directly detecting binary and substellar companions. Some fraction of nearby RV trend systems are expected to be comprised of compact objects that likewise induce a systemic Doppler signal. In this paper, we report the discovery of a white dwarf companion found to orbit the nearby ($\pi = 28.297 \pm 0.066$ mas) G9 V star HD 169889. High-contrast imaging observations using NIRC2 at Keck and LMIRCam at the LBT uncover the ($\Delta H = 9.76 \pm 0.16$, $\Delta L' = 9.60 \pm 0.03$) companion at an angular separation of 0.8'' (28 au). Thirteen years of precise Doppler observations reveal a steep linear acceleration in RV time series and place a dynamical constraint on the companion mass of $M \geq 0.369 \pm 0.010 M_{\odot}$. This "Sirius-like" system adds to the census of white dwarf companions suspected to be missing in the solar neighborhood.

[221] arXiv:1807.06013v1 [pdf, vox]

Does black-hole growth depend on the cosmic environment?

Guang Yang, W. N. Brandt, B. Darvish, C. -T. J. Chen, F. Vito, D. M. Alexander, F. E. Bauer, J. R. Trump
Submitted Monday 16 July 2018 @ 18:00:00 GMT
24 pages, 17 figures, 7 tables. Accepted by MNRAS

It is well known that environment affects galaxy evolution, which is broadly related to supermassive black hole (SMBH) growth. We investigate whether SMBH evolution also depends on host-galaxy local (sub-Mpc) and global ($\approx 1-10$ Mpc) environment. We construct the surface-density field (local environment) and cosmic web (global environment) in the COSMOS field at $z=0.3-3.0$. The environments in COSMOS range from the field to clusters ($M_\mathrm{halo} \lesssim 10^{14}\ M_\odot$), covering the environments where ${\approx 99\%}$ of galaxies in the Universe reside. We measure sample-averaged SMBH accretion rate ($\overline{\mathrm{​BHAR}}$) from X-ray observations, and study its dependence on overdensity and cosmic-web environment at different redshifts while controlling for galaxy stellar mass ($M_\star$). Our results show that $\overline{\mathrm{B​HAR}}$ does not significantly depend on overdensity or cosmic-web environment once $M_\star$ is controlled, indicating that environment-related physical mechanisms (e.g. tidal interaction and ram-pressure stripping) might not significantly affect SMBH growth. We find that $\overline{\mathrm{B​HAR}}$ is strongly related to host-galaxy $M_\star$, regardless of environment.

[222] arXiv:1807.06014v1 [pdf, vox]

Astrophysical black holes

Pedro R. Capelo
Submitted Monday 16 July 2018 @ 18:00:00 GMT
Preprint of the chapter "Astrophysical black holes", to be published in the review volume "Formation of the First Black Holes", Latif, M. and Schleicher, D. R. G., eds., World Scientific Publishing Company, 2018, pp 1-22 [ see https://www.worldsci​entific.com/worldsci​books/10.1142/10652 ]

In this chapter, we introduce the concept of a black hole (BH) and recount the initial theoretical predictions. We then review the possible types of BHs in nature, from primordial, to stellar-mass, to supermassive BHs. Finally, we focus on the latter category and on their intricate relation with their host galaxies.

[223] arXiv:1807.06015v1 [pdf, vox]

ALMA [CI]$^{3}P_{1}-^{3}P​_{0}$ observations of NGC6240: a puzzling molecular outflow, and the role of outflows in the global $α_{\rm CO}$ factor of (U)LIRGs

Claudia Cicone, Paola Severgnini, Padelis P. Papadopoulos, Roberto Maiolino, Chiara Feruglio, Ezequiel Treister, George C. Privon, Zhi-yu Zhang, Roberto Della Ceca, Fabrizio Fiore, Kevin Schawinski, Jeff Wagg
Submitted Monday 16 July 2018 @ 18:00:00 GMT
Accepted for publication in ApJ

We present ALMA and ACA [CI]$^{3}P_{1}-^{3}P​_{0}$ ([CI](1-0)) observations of NGC6240, which we combine with ALMA CO(2-1) and IRAM PdBI CO(1-0) data to study the physical properties of the massive molecular (H$_2$) outflow. We discover that the receding and approaching sides of the H$_2$ outflow, aligned east-west, exceed 10 kpc in their total extent. High resolution ($0.24"$) [CI](1-0) line images surprisingly reveal that the outflow emission peaks between the two AGNs, rather than on either of the two, and that it dominates the velocity field in this nuclear region. We combine the [CI](1-0) and CO(1-0) data to constrain the CO-to-H$_2$ conversion factor ($\alpha_{\rm CO}$) in the outflow, which is on average $2.1\pm1.2~\rm M_{\odot} (K~km~s^{-1}~pc^2)^{​-1}$. We estimate that $60\pm20$ % of the total H$_2$ gas reservoir of NGC6240 is entrained in the outflow, for a resulting mass-loss rate of $\dot{M}_{\rm out}=2500\pm1200~M_{​\odot}~yr^{-1}$ $\equiv 50\pm30$ SFR. This energetics rules out a solely star formation-driven wind, but the puzzling morphology challenges a classic radiative-mode AGN feedback scenario. For the quiescent gas we compute $\langle\alpha_{\rm CO}\rangle = 3.2\pm1.8~\rm M_{\odot} (K~km~s^{-1}~pc^2)^{​-1}$, which is at least twice the value commonly employed for (U)LIRGs. We observe a tentative trend of increasing $r_{21}\equiv L^{\prime}_{\rm CO(2-1)}/L^{\prime}_​{\rm CO(1-0)}$ ratios with velocity dispersion and measure $r_{21}>1$ in the outflow, whereas $r_{21}\simeq1$ in the quiescent gas. We propose that molecular outflows are the location of the warmer, strongly unbound phase that partially reduces the opacity of the CO lines in (U)LIRGs, hence driving down their global $\alpha_{\rm CO}$ and increasing their $r_{21}$ values.

[224] arXiv:1807.06016v1 [pdf, vox]

The Dragonfly Nearby Galaxies Survey. V. HST/ACS Observations of 23 Low Surface Brightness Objects in the Fields of NGC1052, NGC1084, M96, and NGC4258

Yotam Cohen, Pieter van Dokkum, Shany Danieli, Aaron J. Romanowsky, Roberto Abraham, Allison Merritt, Jielai Zhang, Lamiya Mowla, J. M. Diederik Kruijssen, Charlie Conroy, Asher Wasserman
Submitted Monday 16 July 2018 @ 18:00:00 GMT
Submitted to ApJ. All reduced HST images are available upon request

We present HST/ACS imaging of twenty-three very low surface brightness ($\mu_{e,V}$=25-27.5​) galaxies detected in the fields of four nearby galaxy groups. These objects were selected from deep optical imaging obtained with the Dragonfly Telephoto Array. Seven are new discoveries, while most of the others had been identified previously in visual surveys of deep photographic plates and more recent surveys. Few have previously been studied in detail. From the ACS images, we measure distances to the galaxies using both the tip of the red giant branch method and the surface brightness fluctuations method. We demonstrate that the two methods are consistent with each other in the regime where both can be applied. The distances to 15 out of 20 galaxies with stable measurements are consistent with that of the targeted group within errors. This suggests that assuming group membership based solely on projected proximity is ~75% successful in this regime. The galaxies are nearly round, with a median axis ratio of 0.85, and visually resemble dwarf spheroidal galaxies. The objects have a range of sizes, from $R_e$=0.4 kpc to $R_e$=1.8 kpc, with a median of 1.0 kpc. They range in luminosity from $M_V$=-11.4 to $M_V$=-15.6, with a median of -12.4. Galaxies with $R_e$~1 kpc and $M_V$~-12 are fairly rare in the Local Group but we find many of them in this relatively small sample. Four of the objects fall in the class of ultra diffuse galaxies (UDGs), with $R_e$>1.5 kpc and $\mu_{0,V}$>24 mag/arcsec^2, including the recently identified dark matter deficient galaxy NGC1052-DF2.

[225] arXiv:1807.06001v1 [pdf, vox]

A Statistical Study to Determine the Origin of Long-Duration Gamma-ray Flares

Lisa M. Winter, Valerie Bernstein, Nicola Omodei, Melissa Pesce-Rollins
Submitted Monday 16 July 2018 @ 17:57:45 GMT
accepted in the Astrophysical Journal

Two scenarios have been proposed to account for sustained $\ge 30$\,MeV gamma-ray emission in solar flares: (1) prolonged particle acceleration/trappin​g involving large-scale magnetic loops at the flare site, and (2) precipitation of high-energy ($>$ 300 MeV) protons accelerated at coronal/interplaneta​ry shock waves. To determine which of these scenarios is more likely, we examine the associated soft X-ray flares, coronal mass ejections (CMEs), and solar energetic proton events (SEPs) for: (a) the long-duration gamma-ray flares (LDGRFs) observed by the Large Area Telescope (LAT) on \Fermi, and (b) delayed and/or spatially-extended high-energy gamma-ray flares observed by the Gamma-ray Spectrometer on the Solar Maximum Mission, the Gamma-1 telescope on the Gamma satellite, and the Energetic Gamma-Ray Experiment Telescope on the Compton Gamma-Ray Observatory. For the \Fermi data set of 11 LDGRFs with $>$100 MeV emission lasting for $\ge \sim 2$ hours, we search for associations and reverse associations between LDGRFs, X-ray flares, CMEs, and SEPs, i.e., beginning with the gamma-ray flares and also, in turn, with X-class soft X-ray flares, fast ($\ge$ 1500 km s$^{-1}$) and wide CMEs, and intense (peak flux $\ge 2.67 \times 10^{-3}$ protons cm$^{-2}$ s$^{-1}$ sr$^{-1}$, with peak to background ratio $>$ 1.38) $>$ 300 MeV SEPs at 1 A.U. While LDGRFs tend to be associated with bright X-class flares, we find that only 1/3 of the X-class flares during the time of \Fermi monitoring coincide with an LDGRF. However, nearly all fast, wide CMEs are associated with an LDGRF. These preliminary association analyses favor the proton precipitation scenario, although there is a prominent counter-example of a potentially magnetically well-connected solar eruption with $>$ 100 MeV emission for $\sim 10$ h for which the near-Earth $>$ 300 MeV proton intensity did not rise above background.

[226] arXiv:1807.05999v1 [pdf, vox]

The VIMOS Public Extragalactic Redshift Survey (VIPERS): Unbiased clustering estimate with VIPERS slit assignment

F. G. Mohammad, D. Bianchi, W. J. Percival, S. de la Torre, L. Guzzo, B. R. Granett, E. Branchini, M. Bolzonella, B. Garilli, M. Scodeggio, U. Abbas, C. Adami, J. Bel, D. Bottini, A. Cappi, O. Cucciati, I. Davidzon, P. Franzetti, A. Fritz, A. Iovino, J. Krywult, V. Le Brun, O. Le Fèvre, K. Małek, F. Marulli, M. Polletta, A. Pollo, L. A. M. Tasca, R. Tojeiro, D. Vergan, A. Zanichelli, S. Arnouts, J. Coupon, G. De Lucia, O. Ilbert, L. Moscardini, T. Moutard
Submitted Monday 16 July 2018 @ 17:57:08 GMT
15 pages, 13 figures

The VIPERS galaxy survey has measured the clustering of $0.5<z<1.2$ galaxies, enabling a number of measurements of galaxy properties and cosmological redshift-space distortions (RSD). Because the measurements were made using one-pass of the VIMOS instrument on the VLT, the galaxies observed only represent approximately $47\%$ of the parent target sample, with a distribution imprinted with the pattern of the VIMOS slitmask. Correcting for the effect on clustering has previously been achieved using an approximate approach developed using mock catalogues. Pairwise Inverse Probability (PIP) weighting has recently been proposed by Bianchi & Percival to correct for missing galaxies, and we apply it to mock VIPERS catalogues to show that it accurately corrects the clustering for the VIMOS effects, matching the clustering measured from the observed sample to that of the parent. We then apply PIP-weighting to the VIPERS data, and fit the resulting monopole and quadrupole moments of the galaxy two-point correlation function with respect to the line-of-sight, making measurements of RSD. The results are close to previous measurements, showing that the previous approximate methods used by the VIPERS team are sufficient given the errors obtained on the RSD parameter.

[227] arXiv:1807.05995v1 [pdf, vox]

Digital frequency multiplexing with sub-Kelvin SQUIDs

Amy E. Lowitz, Amy N. Bender, Matthew A. Dobbs, Adam J. Gilbert
Submitted Monday 16 July 2018 @ 17:54:12 GMT

Digital frequency multiplexing (dfMux) is a readout architecture for transition edge sensor-based detector arrays and is used on telescopes including SPT-3G, POLARBEAR-2, and LiteBIRD. Here, we present recent progress and plans for development of a sub-Kelvin SQUID architecture for digital frequency multiplexed bolometers. This scheme moves the SQUID from the 4 K stage to the 250 mK stage, adjacent to the bolometers. Operating the SQUID on the detector stage may offer lower noise and greater scalability. Electrical performance will be improved as a result of decreased wiring length and reduced parasitics, allowing for higher multiplexing factors and lower bolometer R_normal . These performance improvements will enable ultra-large focal planes for future instruments such as CMB-S4.

[228] arXiv:1807.05994v1 [pdf, vox]

Constraining the Milky Way Halo Potential with the GD-1 stellar stream

Khyati Malhan, Rodrigo A. Ibata
Submitted Monday 16 July 2018 @ 17:50:11 GMT
11 pages, 8 Figures, 1 Table

We use ESA/Gaia astrometry together with SEGUE measurements of the $70\deg$ long GD-1 stellar stream to explore the improvement on the Galactic gravitational potential that these new data provide. Assuming a realistic universal model for the halo together with reasonable models of the baryonic components, we find that orbital solutions require the circular velocity at the Solar radius to be $V_{\rm circ}(R_\odot) = 244^{+6}_{-2}\,{\rm km\, s^{-1}}$, and also that the density flattening of the halo is $q_{\rho}= 0.86^{+0.04}_{-0.07}​$. The corresponding Galactic mass within $14.5\, {\rm kpc}$, the mean Galactocentric distance of GD-1, is $M_{\rm MW}(<14.5{\rm kpc})=1.75^{+0.06}_{​-0.05} \times 10^{11}\, M_\odot$. Moreover, Gaia's excellent proper motions also allowed us to measure the velocity dispersion of the GD-1 stream in the direction tangential to the line of sight to be $<1.25\,{\rm km\, s^{-1}}$ (90 % confidence limit), confirming the extremely cold dynamical nature of this system.

[229] arXiv:1807.04748v2 [pdf, vox]

Blazar Flares as an Origin of High-Energy Cosmic Neutrinos?

Kohta Murase, Foteini Oikonomou, Maria Petropoulou
Submitted Monday 16 July 2018 @ 17:35:45 GMT
11 pages, 2 figures, 1 table, with clarification in discussions. Results and conclusions unchanged

We consider implications of high-energy neutrino emission from blazar flares, including the recent event IceCube-170922A and the 2014-2015 neutrino flare that could originate from TXS 0506+056. First, we discuss their contribution to the diffuse neutrino intensity taking into account various observational constraints. Blazars are likely to be subdominant in the diffuse neutrino intensity at sub-PeV energies, and we show that blazar flares like those of TXS 0506+056 could make <1-10 percent of the total neutrino intensity. We also argue that the neutrino output of blazars can be dominated by flares in the standard leptonic scenario for their gamma-ray emission, but energetic flares can still be detected with a rate of <1 per year. Second, we consider multi-messenger constraints on the source modeling. We show that luminous neutrino flares should be accompanied by luminous broadband cascade emission, emerging also in X rays and gamma rays. This implies that not only gamma-ray telescopes like Fermi but also X-ray sky monitors such as Swift and MAXI are critical to test the canonical picture based on the single-zone modeling. We also suggest a two-zone model that can satisfy the X-ray constraints, in which the the flaring neutrinos could be produced via either photomeson or hadronuclear process.

[230] arXiv:1807.05986v1 [pdf, vox]

Actions are weak stellar age indicators in the Milky Way disk

Angus Beane, Melissa Ness, Megan Bedell
Submitted Monday 16 July 2018 @ 17:34:02 GMT
12 pages, 10 figures, ApJ submitted; comments welcome. Code and data available at https://github.com/g​usbeane/dyndat . Animated version of Figs. 5 & 6 available at https://www.gusbeane​.com/actions-weak-ag​e

The orbital properties of stars in the disk are signatures of their formation, but they are also expected to change over time due to the dynamical evolution of the Galaxy. Stellar orbits can be quantified by three dynamical actions, J_r, L_z, and J_z, which provide measures of the orbital eccentricity, guiding radius, and non-planarity, respectively. Changes in these dynamical actions over time reflect the strength and efficiency of the evolutionary processes that drive stellar redistributions. We examine how dynamical actions of stars are correlated with their age using two samples of stars with well-determined ages: 78 solar twin stars (with ages to ~5%) and 4376 stars from the APOKASC2 sample (~20%). We compute actions using spectroscopic radial velocities from previous surveys and parallax and proper motion measurements from Gaia DR2. We find weak gradients in all actions with stellar age, of (7.51 +/- 0.52, -29.0 +/- 1.83, 1.54 +/- 0.18) kpc km/s/Gyr for J_r, L_z, and J_z, respectively. There is, however, significant scatter in the action-age relation. We caution that our results will be affected by the restricted spatial extent of our sample, particularly in the case of J_z. Nevertheless, these action-age gradients and their associated variances provide strong constraints on the efficiency of the mechanisms that drive the redistribution of stellar orbits over time and demonstrate that actions are informative as to stellar age. The shallow action-age gradients combined with the large dispersion in each action at a given age, however, renders the prospect of age inference from orbits of individual stars bleak. Using the precision measurements of [Fe/H] and [$\alpha$/Fe] for our stars we investigate the abundance-action relationship and find weak correlations. Similar to our stellar age results, dynamical actions afford little discriminating power between low- and high-$\alpha$ stars.

[231] arXiv:1807.05939v1 [pdf, vox]

Thermodynamics and Chemistry of the Early Universe

Stefano Bovino, Daniele Galli
Submitted Monday 16 July 2018 @ 16:01:56 GMT
Preprint of the Chapter "Thermodynamics and Chemistry of the Early Universe", to be published in the review volume "Formation of the First Black Holes", Latif M. and Schleicher D.R.G., eds., World Scientific Publishing Company, 2018, pp. [see http://www.worldscie​ntific.com/worldscib​ooks/10.1142/10652]

The interplay between chemistry and thermodynamics determines the final outcome of the process of gravitational collapse and sets the conditions for the formation of the first cosmological objects, including primordial supermassive black holes. In this chapter, we will review the main chemical reactions and the most important heating/cooling processes taking place in a gas of primordial composition, including the effects of local and cosmological radiation backgrounds.

[232] arXiv:1807.05925v1 [pdf, vox]

Planetary Nebulae Shaped By Common Envelope Evolution

Adam Frank, Zhuo Chen, Thomas Reichardt, Orsola De Marco, Eric Blackman, Jason Nordhaus
Submitted Monday 16 July 2018 @ 15:36:13 GMT
To be published in proceedings of Aspherical Planetary Nebula 7

The morphologies of planetary nebula have long been believed to be due to wind shaping processes in which a fast wind from the central star impacts a previously ejected envelope. Asymmetries assumed to exist in the slow wind envelope lead to inertial confinement shaping the resulting interacting winds flow. We present new results demonstrating the effectiveness of Common Envelope Evolution (CEE) at producing aspherical envelopes which, when impinged upon by a spherical fast stellar wind, produce highly bipolar, jet-like outflows. We have run two simple cases using the output of a single PHANTOM SPH CEE simulation. Our work uses the Adaptive Mesh Refinement code AstroBEAR to track the interaction of the fast wind and CEE ejecta allowing us to follow the morphological evolution of the outflow lobes at high resolution in 3-D. Our two models bracket low and high momentum output fast winds. We find the interaction leads to highly collimated bipolar outflows. In addition, the bipolar morphology depends on the fast wind momentum injection rate. With this dependence comes the initiation of significant symmetry breaking between the top and bottom bipolar lobes. Our simulations, though simplified, confirm the long-standing belief that CEE can plan a major role in PPN and PN shaping.

[233] arXiv:1807.05922v1 [pdf, vox]

AutoSpec: Fast Automated Spectral Extraction Software for IFU Datacubes

Alex Griffiths, Christopher J. Conselice
Submitted Monday 16 July 2018 @ 15:34:00 GMT
Submitted to ApJ, 8 pages, 4 figures

With the ever growing popularity of integral field unit (IFU) spectroscopy, countless observations are being performed over multiple object systems such as blank fields and galaxy clusters. With this, an increasing amount of time is being spent extracting one dimensional object spectra from large three dimensional datacubes. However, a great deal of information available within these datacubes is overlooked in favor of photometrically based spatial information. Here we present a novel, yet simple approach of optimal source identification, utilizing the wealth of information available within an IFU datacube, rather than relying on ancillary imaging. We show that we are able to obtain object spectra comparable or superior to manual extractions. Further, implementing our custom designed algorithms also improves the signal-to-noise of the extracted spectra and successfully deblends sources from nearby contaminants. This will be a critical tool for future IFU observations of blank and deep fields, especially over large areas where automation is necessary. We implement these techniques into the Python based spectral extraction software, AutoSpec which is available via GitHub at: https://github.com/a​-griffiths/AutoSpec

[234] arXiv:1807.05916v1 [pdf, vox]

On Inflationary Scale, Reheating Scale and Pre-BBN Cosmology with Scalar Fields

Alessandro Di Marco, Gianfranco Pradisi, Paolo Cabella
Submitted Monday 16 July 2018 @ 15:21:10 GMT
10 pages, 4 figures

In this paper, we discuss the constraints on the reheating temperature supposing an early post-reheating cosmological phase dominated by one or more simple scalar fields produced from inflaton decay and decoupled from matter and radiation. In addition, we explore the combined effects of the reheating and non-standard scalar field phases on the inflationary number of $e$-foldings.

[235] arXiv:1807.05909v1 [pdf, vox]

Hypervelocity stars in the Gaia era: Runaway B stars beyond the speed limit of classical ejection mechanisms

Andreas Irrgang, Simon Kreuzer, Ulrich Heber
Submitted Monday 16 July 2018 @ 15:03:56 GMT
Submitted to A&A (Astronomy and Astrophysics)

Young massive stars in the halo are supposed to be runaway stars from the Galactic disk. Possible ejection scenarios are binary supernova ejections (BSE) or dynamical ejections from star clusters (DE). Hypervelocity stars (HVSs) are extreme runaway stars that are potentially unbound to the Galaxy. Powerful acceleration mechanisms like the tidal disruption of a binary by a supermassive black hole are required. Hence, HVSs are believed to originate in the Galactic center (GC). Gaia DR2 offers the opportunity to study HVSs in an unprecedented manner. We revisit the most interesting HVSs, i.e., 15 stars for which proper motions with the Hubble Space Telescope were obtained in the pre-Gaia era, to unravel their origin. By carrying out kinematic analyses in three different Galactic mass models, kinematic properties are obtained that help to constrain the spatial origins of the HVSs. While HVSs previously considered unbound remain unbound in two Galactic potentials, most stars become bound in the most massive Galactic model. For nine stars (including five unbound candidates), the GC can be ruled out as spatial origin at $2\sigma$ confidence. Using optical and infrared photometry to determine its spectrophotometric distance, we confirm that HVS3 originates in the Large Magellanic Cloud. Our results suggest that a large fraction of the HVSs are actually disk runaway stars launched close to or beyond Galactic escape velocities. Population synthesis models predict that only a small fraction of the HVSs stems from BSE. Furthermore, a maximum ejection velocity of 540\,km/s is predicted for BSE and a similar limit has been found for DE. The ejection velocities of five of our non-GC HVSs are close to or above this limit, calling for the existence of another dynamical ejection mechanism (e.g., massive perturbers such as intermediate mass black holes) besides the classical scenarios mentioned above.

[236] arXiv:1807.05901v1 [pdf, vox]

Dynamical evolution of triple-star systems by Lidov-Kozai cycles and tidal friction

Manon Bataille, Anne-Sophie Libert, Alexandre C. M. Correia
Submitted Monday 16 July 2018 @ 14:56:03 GMT
Accepted for publication in MNRAS

Many triple-star systems have an inner pair with an orbital period of a few days only. A common mechanism to explain the short-period pile-up present in the observations is the migration through Lidov-Kozai cycles combined with tidal friction. Here, we revisit this mechanism and aim to determine the initial orbital configurations leading to this process. We show that the mutual inclination of the triple-star system is not the only critical parameter, since the eccentricity as well as the argument of the pericenter of the inner orbit also play an important role in the establishment of the Lidov-Kozai migration. Our framework is the secular hierarchical three-body problem (octupole order approximation) with general relativity corrections, including the effects of tides, stellar oblateness and magnetic spin-down braking. Both the orbital and the spin evolutions are considered. Extensive numerical simulations with uniform and non-uniform distributions of the initial orbital parameters are carried out, and unbiased initial conditions leading to Lidov-Kozai migration are revealed. Finally, we highlight the importance of the initial "Kozai constant" $h=\sqrt{(1-e^2)}\co​s{i}$ in the dynamical evolution of triple-star systems, by showing that phase portraits at given $h$-values unveil different evolution paths.

[237] arXiv:1807.05898v1 [pdf, vox]

The orbital architecture and debris disks of the HR 8799 planetary system

Krzysztof Gozdziewski, Cezary Migaszewski
Submitted Monday 16 July 2018 @ 14:50:10 GMT
27 pages, 13 figures, 1 table; accepted in Astrophysical Journal Supplement Series

The HR8799 planetary system with four ~10 mJup planets in wide orbits up to 70 au, and periods up to 500 yr has been detected with the direct imaging. Its intriguing orbital architecture is not fully resolved due to time-limited astrometry covering ~20 years. Earlier, we constructed a heuristic model of the system based on rapid, convergent migration of the planets. We developed a better structured and CPU-efficient variant of this model. We re-analyzed the self-consistent, homogeneous astrometric dataset in Konopacky (2016). The best-fitting configuration agrees with our earlier findings. The planets are likely involved in dynamically robust Laplace resonance chain. Hypothetical planets with masses below the current detection limit of 0.1-3 Jupiter masses, within the observed inner, or beyond the outer orbit, respectively, do not influence the long term stability of the system. We predict positions of such non-detected objects. The long-term stable orbital model of the observed planets helps to simulate the dynamical structure of debris disks in the system. A CPU-efficient fast indicator technique makes it possible to reveal their complex, resonant shape in 10^6 particles scale. We examine the inner edge of the outer disk detected between 90-145 au. We also reconstruct the outer disk assuming that it has been influenced by convergent migration of the planets. A complex shape of the disk strongly depends on various dynamical factors, like orbits and masses of non-detected planets. It may be highly non-circular and its models are yet non-unique, regarding both observational constraints, as well as its origin.

[238] arXiv:1807.05895v1 [pdf, vox]

Non-thermal emission from stellar bow shocks

Maria Victoria del Valle, Martin Pohl
Submitted Monday 16 July 2018 @ 14:43:43 GMT
18 pages, 12 figures. Accepted for publication in ApJ

Since the detection of non-thermal radio emission from the bow shock of the massive runaway star BD +43$^{\circ}$3654 simple models have predicted high-energy emission, at X and gamma-rays, from these Galactic sources. Observational searches for this emission so far give no conclusive evidence but a few candidates at gamma rays. In this work we aim at developing a more sophisticated model for the non-thermal emission from massive runaway star bow shocks. The main goal is to establish whether these systems are efficient non-thermal emitters, even if they are not strong enough to be yet detected. For modeling the collision between the stellar wind and the interstellar medium we use 2D hydrodynamic simulations. We then adopt the flow profile of the wind and the ambient medium obtained with the simulation as the plasma state for solving the transport of energetic particles injected in the system, and the non-thermal emission they produce. For this purpose we solve a 3D (2 spatial + energy) advection-diffusion equation in the test-particle approximation. We find that a massive runaway star with a powerful wind converts 0.16-0.4% of the power injected in electrons into non-thermal emission, mostly produced by inverse Compton scattering of dust-emitted photons by relativistic electrons, and secondly by synchrotron radiation. This represents a fraction of $\sim$ $10^{-5}-10^{-4}$ of the wind kinetic power. Given the better sensibility of current instruments at radio wavelengths theses systems are more prone to be detected at radio through the synchrotron emission they produce rather than at gamma energies.

[239] arXiv:1807.05888v1 [pdf, vox]

Discovery of extended main sequence turn offs in Galactic open clusters

A. F. Marino, A. P. Milone, L. Casagrande, N. Przybilla, L. Balaguer-Nunez, A. Serenelli, F. Vilardell
Submitted Monday 16 July 2018 @ 14:34:10 GMT
9 pages, 4 figures, Submitted to ApJ

By far, the color-magnitude diagrams (CMDs) of Galactic open clusters have been considered proto-types of single stellar populations. By using photometry in ultraviolet and optical bands we discovered that the nearby young cluster NGC6705 (M11) exhibits an extended main-sequence turn off (eMSTO) and a broadened main-sequence (MS). This is the first evidence of multiple stellar populations in a Galactic open cluster. By using high-resolution VLT spectra we provide direct evidence that the multiple sequences along the CMD correspond to stellar populations with different rotation rates. Specifically, the blue MS is formed of slow-rotating stars, while red-MS stars are fast rotators. Moreover, we exploit photometry from Gaia DR2 to show that three Galactic open clusters, namely NGC2099, NGC2360, and NGC2818, exhibit the eMSTO, thus suggesting that it is a common feature among these objects. Our previous work on the Large Magellanic Cloud star cluster NGC1818 shows that slowly and fastly-rotating stars populate the blue and red MS observed in its CMD. The similarities between M11 and the young clusters of the Magellanic Clouds suggest that rotation is responsible for the appearance of multiple populations in the CMDs of both Milky Way open clusters and Magellanic Clouds young clusters.

[240] arXiv:1807.05865v1 [pdf, vox]

EPIC 220501947 b and K2-237 b: two transiting hot Jupiters

A. M. S. Smith, Sz. Csizmadia, D. Gandolfi, S. Albrecht, R. Alonso, O. Barragán, J. Cabrera, W. D. Cochran, F. Dai, H. Deeg, Ph. Eigmüller, M. Endl, A. Erikson, M. Fridlund, A. Fukui, S. Grziwa, E. W. Guenther, A. P. Hatzes, D. Hidalgo, T. Hirano, J. Korth, M. Kuzuhara, J. Livingston, N. Narita, D. Nespral, P. Niraula, G. Nowak, E. Palle, M. Pätzold, C. M. Persson, J. Prieto-Arranz, H. Rauer, S. Redfield, I. Ribas, V. Van Eylen
Submitted Monday 16 July 2018 @ 13:53:45 GMT
11 pages, 11 figures, submitted to MNRAS

We report the discovery from K2 of two transiting hot Jupiter systems. EPIC 220501947 (observed in Campaign 8) is a K5 dwarf which hosts a planet slightly smaller than Jupiter, orbiting with a period of 4.0 d. We have made an independent discovery of K2-237 b (Campaign 11), which orbits an F6 dwarf every 2.2 d and has an inflated radius 50 - 60 per cent larger than that of Jupiter. We use high-precision radial velocity measurements, obtained using the HARPS and FIES spectrographs, to measure the planetary masses. We find that EPIC 220501947 b has a similar mass to Saturn, while K2-237 b is a little more massive than Jupiter.

[241] arXiv:1807.05825v1 [pdf, vox]

Revisiting the connection between magnetic activity, rotation period, and convective turnover time for main-sequence stars

M. Mittag, J. H. M. M. Schmitt, K. -P. Schröder
Submitted Monday 16 July 2018 @ 12:55:31 GMT
13 pages, 7 figures, accepted for publication in A&A

The connection between stellar rotation, stellar activity, and convective turnover time is revisited with a focus on the sole contribution of magnetic activity to the Ca II H&K emission, the so-called excess flux, and its dimensionless indicator R$^{+}_{\rm{HK}}$ in relation to other stellar parameters and activity indicators. Our study is based on a sample of 169 main-sequence stars with directly measured Mount Wilson S-indices and rotation periods. The R$^{+}_{\rm{HK}}$ values are derived from the respective S-indices and related to the rotation periods in various $B-V$-colour intervals. First, we show that stars with vanishing magnetic activity, i.e. stars whose excess flux index R$^{+}_{\rm{HK}}$ approaches zero, have a well-defined, colour-dependent rotation period distribution; we also show that this rotation period distribution applies to large samples of cool stars for which rotation periods have recently become available. Second, we use empirical arguments to equate this rotation period distribution with the global convective turnover time, which is an approach that allows us to obtain clear relations between the magnetic activity related excess flux index R$^{+}_{\rm{HK}}$, rotation periods, and Rossby numbers. Third, we show that the activity versus Rossby number relations are very similar in the different activity indicators. As a consequence of our study, we emphasize that our Rossby number based on the global convective turnover time approaches but does not exceed unity even for entirely inactive stars. Furthermore, the rotation-activity relations might be universal for different activity indicators once the proper scalings are used.

[242] arXiv:1807.05802v1 [pdf, vox]

Infrared variability of radio-loud narrow-line Seyfert 1 galaxies

K. É. Gabányi, A. Moór, S. Frey
Submitted Monday 16 July 2018 @ 11:44:58 GMT
Accepted for publication in Proceedings of Science for the conference "Revisiting narrow-line Seyfert 1 galaxies and their place in the Universe" (Padova, April 2018)

Most of the radio-loud narrow-line Seyfert 1 (NLS1) galaxies resemble compact steep-spectrum sources. However, the extremely radio-loud ones show blazar-like characteristics, like flat radio spectra, compact radio cores, substantial variability and high brightness temperatures. These objects are thought to be similar to blazars as they possess relativistic jets seen at small angle to the line of sight. This claim has been further supported by the Fermi satellite discovery of gamma-ray emission from a handful of these sources. Using the Wide-Field Infrared Survey Explorer (WISE) data, we analyzed the mid-infrared variability characteristics of $42$ radio-loud NLS1 at $3.4$ and $4.6\,\mu$m. We found that $27$ out of the studied $42$ sources showed variability in at least one of the two infrared bands. In some cases, significant changes in the infrared colors can alter the location of the source in the WISE color-color diagram which might lead to different classification. More than $60$% of the variable sources also showed variability within a $1-1.5$ day interval. Such short time scales argue for a compact emission region like those associated with the jets. This connection is further strengthened by the fact that the brightest $\gamma$-ray emitters of the sample ($6$ sources), all showed short time scale infrared variability.

[243] arXiv:1807.04293v2 [pdf, vox]

The Galactic WC and WO stars: The impact of revised distances from Gaia DR2 and their role as massive black hole progenitors

Andreas A. C. Sander, Wolf-Rainer Hamann, Helge Todt, Rainer Hainich, Tomer Shenar, Varsha Ramachandran, Lidia M. Oskinova
Submitted Monday 16 July 2018 @ 11:11:39 GMT
17 pages, 10 figures, 6 tables; submitted to A&A

Wolf-Rayet stars of the carbon sequence (WC stars) are an important cornerstone in the late evolution of massive stars before their core collapse. As core-helium burning, hydrogen-free objects with huge mass-loss, they are likely the last observable stage before collapse and thus promising progenitor candidates for type Ib/c supernovae. Their strong mass-loss furthermore provides challenges and constraints to the theory of radiatively driven winds. Thus, the determination of the WC star parameters is of major importance for several astrophysical fields. With Gaia DR2, for the first time parallaxes for a large sample of Galactic WC stars are available, removing major uncertainties inherent to earlier studies. In this work, we re-examine the sample from Sander et al. (2012) to derive key properties of the Galactic WC population. All quantities depending on the distance are updated, while the underlying spectral analyses remain untouched. Contrasting earlier assumptions, our study yields that WC stars of the same subtype can significantly vary in absolute magnitude. With Gaia DR2, the picture of the Galactic WC population becomes more complex: We obtain luminosities ranging from log L = 4.9 to 6.0 with one outlier having log L = 4.7. This indicates that the WC stars are likely formed from a broader initial mass range than previously assumed. We obtain mass-loss rates ranging between log Mdot = -5.1 and -4.1, with Mdot propto L^0.68 and a linear scaling of the modified wind momentum with luminosity. We discuss the implications for stellar evolution, including unsolved issues regarding the need of envelope inflation to address the WR radius problem, and the open questions in regard to the connection of WR stars with Gamma-ray bursts. WC and WO stars are progenitors of massive black holes, collapsing either silently or in a supernova that most-likely has to be preceded by a WO stage.

[244] arXiv:1807.05784v1 [pdf, vox]

Modelling mid-infrared molecular emission lines from T Tauri stars

P. Woitke, M. Min, W. -F. Thi, C. Roberts, A. Carmona, I. Kamp, F. Menard, C. Pinte
Submitted Monday 16 July 2018 @ 10:47:03 GMT
accepted by A&A, 13 figures, 4 tables

We introduce a new modelling framework called FLiTs to simulate infrared line emission spectra from protoplanetary discs. This paper focuses on the mid-IR spectral region between 9.7 um to 40 um for T Tauri stars. The generated spectra contain several tens of thousands of molecular emission lines of H2O, OH, CO, CO2, HCN, C2H2, H2 and a few other molecules, as well as the forbidden atomic emission lines of SI, SII, SIII, SiII, FeII, NeII, NeIII, ArII and ArIII. In contrast to previously published works, we do not treat the abundances of the molecules nor the temperature in the disc as free parameters, but use the complex results of detailed 2D ProDiMo disc models concerning gas and dust temperature structure, and molecular concentrations. FLiTs computes the line emission spectra by ray tracing in an efficient, fast and reliable way. The results are broadly consistent with R=600 Spitzer/IRS observational data of T Tauri stars concerning line strengths, colour, and line ratios. In order to achieve that agreement, however, we need to assume either a high gas/dust mass ratio of order 1000, or the presence of illuminated disc walls at distances of a few au. The molecules in these walls cannot be photo-dissociated easily by UV because of the large densities in the walls which favour their re-formation. Most observable molecular emission lines are found to be optically thick, rendering a standard analysis with column densities difficult. We find that the difference between gas and dust temperatures in the disc surface is important for the line formation. We briefly discuss the effects of C/O ratio and choice of chemical rate network on these results. Our analysis offers new ways to infer the chemical and temperature structure of T Tauri discs from future JWST/MIRI observations, and to possibly detect secondary illuminated disc walls based on their specific mid-IR molecular signature.

[245] arXiv:1807.05768v1 [pdf, vox]

First Detection of the Simplest Organic Acid in a Protoplanetary Disk

Cécile Favre, Davide Fedele, Dmitry Semenov, Sergey Parfenov, Claudio Codella, Cecilia Ceccarelli, Edwin A. Bergin, Edwige Chapillon, Leonardo Testi, Franck Hersant, Bertrand Lefloch, Francesco Fontani, Geoffrey A. Blake, L. Ilsedore Cleeves, Chunhua Qi, Kamber R. Schwarz, Vianney Taquet
Submitted Monday 16 July 2018 @ 10:15:18 GMT
9 pages, 4 figures, 1 table, published online in ApJL on 16th July 2018

The formation of asteroids, comets and planets occurs in the interior of protoplanetary disks during the early phase of star formation. Consequently, the chemical composition of the disk might shape the properties of the emerging planetary system. In this context, it is crucial to understand whether and what organic molecules are synthesized in the disk. In this Letter, we report the first detection of formic acid (HCOOH) towards the TW Hydrae protoplanetary disk. The observations of the trans-HCOOH 6$_{(1,6)-5(1,5)}$ transition were carried out at 129~GHz with ALMA. We measured a disk-averaged gas-phase t-HCOOH column density of $\sim$ (2-4)$\times$10$^{12​}$~cm$^{-2}$, namely as large as that of methanol. HCOOH is the first organic molecules containing two oxygen atoms detected in a protoplanetary disk, a proof that organic chemistry is very active even though difficult to observe in these objects. Specifically, this simplest acid stands as the basis for synthesis of more complex carboxylic acids used by life on Earth.

[246] arXiv:1807.05767v1 [pdf, vox]

Statistical analysis of UV spectra of a quiescent prominence observed by IRIS

S. Jejčič, P. Schwartz, P. Heinzel, M. Zapiór, S. Gunár
Submitted Monday 16 July 2018 @ 10:15:08 GMT
13 pages, 21 figures

The paper analyzes the structure and dynamics of a quiescent prominence that occurred on October 22, 2013. We aim to determine the physical characteristics of the observed prominence using MgII k and h, CII (1334 and 1336 A), and SiIV (1394 A) lines observed by IRIS. We employed the 1D non-LTE modeling of MgII lines assuming static isothermal-isobaric slabs. We selected a large grid of models with realistic input parameters and computed synthetic MgII lines. The method of Scargle periodograms was used to detect possible prominence oscillations. We analyzed 2160 points of the observed prominence in five different sections along the slit averaged over ten pixels due to low signal to noise ratio in the CII and SiIV lines. We computed the integrated intensity for all studied lines, while the central intensity and reversal ratio was determined only for both MgII and CII 1334 lines. We plotted several correlations: time evolution of the integrated intensities and central intensities, scatter plots between all combinations of line integrated intensities, and reversal ratio as a function of integrated intensity. We also compared MgII observations with the models. Results show that more than two-thirds of MgII profiles and about one-half of CII 1334 profiles are reversed. Profiles of SiIV are generally unreversed. The MgII and CII lines are optically thick, while the SiIV line is optically thin. The studied prominence shows no global oscillations in the MgII and CII lines. Therefore, the observed time variations are caused by random motions of fine structures with velocities up to 10 km/s. The observed average ratio of MgII k to MgII h line intensities can be used to determine the prominence's characteristic temperature. Certain disagreements between observed and synthetic line intensities of MgII lines point to the necessity of using more complex 2D multi-thread modeling in the future.

[247] arXiv:1807.05760v1 [pdf, vox]

Growth problems of stellar black holes in early galaxies

Maria Carmela Orofino, Andrea Ferrara, Simona Gallerani
Submitted Monday 16 July 2018 @ 09:45:14 GMT
12 pages, 11 figures

The nature of the seeds of the observed high-z super-massive black holes (SMBH) is unknown. Although different options have been proposed, involving e.g. intermediate mass direct collapse black holes, BH remnants of massive stars remain the most natural explanation. To identify the most favorable conditions (if any) for their rapid growth, we study the accretion rate of a M_BH = 100M_sun BH formed in a typical z = 10 galaxy under different conditions (e.g. galaxy structure, BH initial position and velocity). We model the galaxy baryonic content and follow the BH orbit and accretion history for 300 Myr (the time span in 10 > z > 7), assuming the radiation-regulated accretion model by Park & Ricotti (2013). We find that, within the limits of our model, BH seeds cannot grow by more than 30 percent, suggesting that accretion on light-seed models are inadequate to explain high-z SMBH. We also compute the X-ray emission from such accreting stellar BH population in the (0.5, 8) keV band and find it comparable to the one produced by high-mass X-ray binaries. This study suggests that early BHs, by X-ray pre-heating of the intergalactic medium at cosmic dawn, might leave a specific signature on the HI 21 cm line power spectrum potentially detectable with SKA.

[248] arXiv:1807.05733v1 [pdf, vox]

Pipeline Collector: gathering performance data for distributed astronomical pipelines

Alexandar P. Mechev, Aske Plaat, J. B. Raymond Oonk, Huib T. Intema, Huub J. A. Röttgering
Submitted Monday 16 July 2018 @ 08:54:54 GMT
15 pages, 14 figures, Astronomy and Computing, 2018, ISSN 2213-1337

Modern astronomical data processing requires complex software pipelines to process ever growing datasets. For radio astronomy, these pipelines have become so large that they need to be distributed across a computational cluster. This makes it difficult to monitor the performance of each pipeline step. To gain insight into the performance of each step, a performance monitoring utility needs to be integrated with the pipeline execution. In this work we have developed such a utility and integrated it with the calibration pipeline of the Low Frequency Array, LOFAR, a leading radio telescope. We tested the tool by running the pipeline on several different compute platforms and collected the performance data. Based on this data, we make well informed recommendations on future hardware and software upgrades. The aim of these upgrades is to accelerate the slowest processing steps for this LOFAR pipeline. The pipeline collector suite is open source and will be incorporated in future LOFAR pipelines to create a performance database for all LOFAR processing.

[249] arXiv:1807.05712v1 [pdf, vox]

Narrow Line Seyfert 1s in the IBISCO sample

Manuela Molina, Angela Malizia, Fabrizio Fiore, Chiara Feruglio
Submitted Monday 16 July 2018 @ 08:00:01 GMT
4 pages, 2 figures, 1 table. Proceedings of the conference "Revisiting narrow-line Seyfert 1 galaxies and their place in the Universe ", Padova 9-13 April 2018

We present the broad-band soft and hard X-ray spectral analysis of 8 Narrow Line Seyfert 1 galaxies extracted from the IBISCO Sample. The study also focuses on the properties of the NLS1 in our sample in relation to those of the IBISCO parent Seyfert population. The IBISCO sample comprises 57 AGN selected from the INTEGRAL IBIS AGN catalogue (in the 20-100 keV band), with z$<$0.05 and covering a wide range of luminosities, BH masses and absorption. All AGN have also measurements of the molecular gas (H$_2$) content of their host galaxies, through the detection of CO emission lines. The main goals of this analysis are to accurately determine the X-ray continuum emission, investigate the presence of absorption features around 7 keV (indicative of the presence of outflows) and measure the bolometric luminosity in order to study the accretion parameters of the eight IBISCO NLS1, and study the accretion mechanisms and investigate the feeding and feedback cycle in these peculiar AGN. Preliminary results show that NLS1 tend to have higher Eddington ratios and larger molecular gas fractions than their parent Seyfert population in the IBISCO sample. Nuclear (AGN) vs. host galaxy properties scaling relations of NLS1 in relation to the parent Seyfert population are also explored.

[250] arXiv:1807.05704v1 [pdf, vox]

Studying Dynamical Models of the Core Galaxy NGC 1399 with Merging Remnants

Li-Chin Yeh, Ing-Guey Jiang
Submitted Monday 16 July 2018 @ 07:07:49 GMT
23 pages, accepted by RAA, the remnant ring proposed here might be traced by the dust rings modeled in arXiv:1804.10207

An investigation on the possible dynamical models of the core galaxy NGC 1399 is performed. Because early-type galaxies are likely to be formed through merging events, remnant rings are considered in the modeling process. A numerical survey over three parameters is employed to obtain the best-fit models that are completely consistent with observations. It is found that the inner slope of dark matter profile is a cuspy one for this core galaxy. The existence of remnant rings in best-fit models indicates a merging history. The remnant ring explains the flatten surface brightness, and thus could be the physical counterpart of the core structure of NGC 1399.

[251] arXiv:1807.05693v1 [pdf, vox]

On the discovery of K-enhanced and possibly Mg-depleted stars throughout the Milky Way

Alex J. Kemp, Andrew R. Casey, Matthew T. Miles, Brodie J. Norfolk, John C. Lattanzio, Amanda I. Karakas, Kevin C. Schlaufman, Anna Y. Q. Ho, Christopher A. Tout, Melissa Ness, Alexander P. Ji
Submitted Monday 16 July 2018 @ 06:30:50 GMT

Stars with unusual elemental abundances offer clues about rare astrophysical events or nucleosynthetic pathways. Stars with significantly depleted magnesium and enhanced potassium ([Mg/Fe] < -0.5; [K/Fe] > 1) have to date only been found in the massive globular cluster NGC 2419 and, to a lesser extent, NGC 2808. The origin of this abundance signature remains unknown, as does the reason for its apparent exclusivity to these two globular clusters. Here we present 112 field stars, identified from 454,180 LAMOST giants, that show significantly enhanced [K/Fe] and possibly depleted [Mg/Fe] abundance ratios. Our sample spans a wide range of metallicities (-1.5 < [Fe/H] < 0.3), yet none show abundance ratios of [K/Fe] or [Mg/Fe] that are as extreme as those observed in NGC 2419. If confirmed, the identified sample of stars represents evidence that the nucleosynthetic process producing the anomalous abundances ratios of [K/Fe] and [Mg/Fe] probably occurs at a wide range of metallicities. This would suggest that pollution scenarios that are limited to early epochs (such as Population III supernovae) are an unlikely explanation, although they cannot be ruled out entirely. This sample is expected to help guide modelling attempts to explain the origin of the Mg-K abundance signature.

[252] arXiv:1807.05681v1 [pdf, vox]

CO (7-6), [CI] 370 micron and [NII] 205 micron Line Emission of the QSO BRI 1335-0417 at Redshift 4.407

Nanyao Lu, Tianwen Cao, Tanio Diaz-Santos, Yinghe Zhao, George C. Privon, Cheng Cheng, Yu Gao, C. Kevin Xu, Vassilis Charmandaris, Dimitra Rigopoulou, Paul P. van der Werf, Jiasheng Huang, Zhong Wang, Aaron S. Evans, David B. Sanders
Submitted Monday 16 July 2018 @ 05:15:36 GMT
14 pages, 7 figures; accepted for publication in the Astrophysical Journal

We present the results from our Atacama Large Millimeter/submillim​eter Array (ALMA) imaging observations of the CO (7-6), [CI] 370 um (hereafter [CI]) and [NII] 205 um (hereafter [NI]I) lines and their underlying continuum emission of BRI 1335-0417, an infrared bright quasar at z = 4.407. At the achieved resolutions of 1.1" to 1.2" (or 7.5 to 8.2 kpc), the continuum at 205 and 372 um (rest-frame), the CO (7-6), and the [CI] emissions are at best barely resolved whereas the [NII] emission is well resolved with an ALMA beam de-convolved major axis of 1.3" (+/- 0.3") or 9 (+/-2) kpc. As a warm dense gas tracer, the CO (7-6) emission shows a more compact spatial distribution and a significantly higher peak velocity dispersion than the other two lines that probe lower density gas, a picture favoring a merger-triggered star formation (SF) scenario over an orderly rotating SF disk. The CO (7-6) data also indicate a possible QSO-driven gas outflow that reaches a maximum line-of-sight velocity of 500 to 600 km/s. The far-infrared (FIR) dust temperature (T_dust) of 41.5 K from a gray-body fit to the continuum agrees well with the average T_dust inferred from various line luminosity ratios. The resulting L_CO(7-6)/L_FIR luminosity ratio is consistent with that of local luminous infrared galaxies powered predominantly by SF. The CO(7-6) luminosity-inferred SF rate is 5.1 (+/-1.5) x 10^3 M_solar/yr . The system has an effective star-forming region of 1.7 (+1.7/-0.8) kpc in diameter and a molecular gas reservoir of ~5 x 10^{11} M_solar.

[253] arXiv:1807.04759v2 [pdf, vox]

Ghost of a Shell: Magnetic Fields of Galactic Supershell GSH 006$-$15$+$7

Alec J. M. Thomson, N. M. McClure-Griffiths, Christoph Federrath, John M. Dickey, Ettore Carretti, B. M. Gaensler, Marijke Haverkorn, M. J. Kesteven, Lister Staveley-Smith
Submitted Monday 16 July 2018 @ 04:27:36 GMT
Accepted for publication in Monthly Notices of the Royal Astronomical Society. 19 pages, 19 figures

We identify a counterpart to a Galactic supershell in diffuse radio polarisation, and use this to determine the magnetic fields associated with this object. GSH 006$-$15$+$7 has perturbed the polarised emission at 2.3$\,$GHz, as observed in the S-band Polarisation All Sky Survey (S-PASS), acting as a Faraday screen. We model the Faraday rotation over the shell, and produce a map of Faraday depth over the area across it. Such models require information about the polarised emission behind the screen, which we obtain from the Wilkinson Microwave Anisotropy Probe (WMAP), scaled from 23$\,$GHz to 2.3$\,$GHz, to estimate the synchrotron background behind GSH 006$-$15$+$7. Using the modelled Faraday thickness we determine the magnitude and the plane-of-the-sky structure of the line-of-sight magnetic field in the shell. We find a peak line-of-sight field strength of $|B_\parallel|_\text​{peak} = 2.0\substack{+0.01 \\ -0.7}\,\mu$G. Our measurement probes weak magnetic fields in a low-density regime (number densities of $\sim0.4\,$cm$^{-3}$​) of the ISM, thus providing crucial information about the magnetic fields in the partially-ionised phase.

[254] arXiv:1807.05667v1 [pdf, vox]

A standard siren measurement of the Hubble constant from GW170817 without the electromagnetic counterpart

M. Fishbach, R. Gray, I. Magaña Hernandez, H. Qi, A. Sur, members of the LIGO Scientific Collaboration, the Virgo Collaboration
Submitted Monday 16 July 2018 @ 03:31:37 GMT
9 pages, 5 figures

We perform a statistical standard siren analysis of GW170817. Our analysis does not utilize knowledge of NGC 4993 as the unique host galaxy of the optical counterpart to GW170817. Instead, we consider each galaxy within the GW170817 localization region as a potential host; combining the $H_0$ values from all the galaxies provides a final measurement of $H_0$. We explore the dependence of our results on the galaxy thresholds, as well as the impact of weighting the galaxies by stellar mass and star-formation rate. Considering all galaxies brighter than $0.01 L^\star_B$ (containing $\sim99\%$ of the total blue luminosity) as equally likely to host a BNS merger, we find $H_0= 76^{+48}_{-23}$ km s$^{-1}$ Mpc$^{-1}$ (maximum a posteriori and 68.3% highest density posterior interval; all results are from publicly available LIGO/Virgo sky maps using approximations to the line-of-sight distance distributions). Restricting only to galaxies brighter than $0.626 L^\star_B$ (containing $\sim50\%$ of the total blue luminosity) tightens the measurement to $H_0= 77^{+37}_{-18}$ km s$^{-1}$ Mpc$^{-1}$. We show that weighting the host galaxies by stellar mass or star-formation rate provides entirely consistent results with potentially tighter constraints. While these statistical estimates are inferior to the value from the counterpart standard siren measurement utilizing NGC 4993 as the unique host, our analysis is a proof-of-principle demonstration of the statistical approach first proposed by Bernard Schutz over 30 years ago. This method is of particular promise in the case of binary black holes, since they are not expected to have optical counterparts, and they occur at sufficient rates that the combined statistical standard siren measurements from many events may offer precision measurements of the luminosity distance-redshift relation to high ($z\lesssim1$) redshift.

[255] arXiv:1807.05659v1 [pdf, vox]

Time Asymmetry of Cosmic Background Evolution in Loop Quantum Cosmology

Wen-Hsuan Lucky Chang, Jiun-Huei Proty Wu
Submitted Monday 16 July 2018 @ 02:34:55 GMT
7 pages, with 7 figures and 4 tables

We discuss the asymmetry of cosmic background evolution in time with respect to the quantum bounce in the Loop Quantum Cosmology (LQC), employing the newly proposed bouncing parameter $\alpha_{\rm s}$. We use the Chaotic and the $R^2$ potentials to demonstrate that a possible deflation before the bounce may counteract the inflation that is needed for resolving the cosmological conundrums, so a certain level of time asymmetry is required for the models in LQC. This $\alpha_{\rm s}$ is model dependent and closely related to the amounts of deflation and inflation, so we may use observations to confine $\alpha_{\rm s}$ and thus the model parameters. With further studies this formalism should be useful in providing an observational testbed for the LQC models.

[256] arXiv:1807.05657v1 [pdf, vox]

Visualizing the Hidden Features of Galaxy Morphology with Machine Learning

Jia-Ming Dai, Jizhou Tong
Submitted Monday 16 July 2018 @ 02:08:05 GMT
7 pages, 8 figures

We train three convolutional neural networks (CNNs) to classify galaxies with Galaxy Zoo 2 dataset and extract the activations from the last fully connected layer or the last average pooling layer of CNNs to study the high-dimensional abstract feature representations of galaxy images. We apply t-Distributed Stochastic Neighbour Embedding (t-SNE), a popular dimensionality reduction technique, to visualize the high-dimensional galaxy feature representations in two-dimensional scatter plots. From the visualization, we try to understand the galaxy images data itself and obtain some highly valuable insights. For instance, the learned galaxy feature representations from networks indicate that the galaxies belonging to the same class tend to group together, i.e. same morphological galaxies are clustered; The cluster of completely round smooth galaxy and the cluster of in-between smooth galaxy (between completely round and cigar-shaped) are moved closer, compared to other clusters; The cluster of cigar-shaped smooth galaxy and the cluster of edge-on galaxy are intertwined surprisingly; A galaxy mislabelled as spiral galaxy in the original dataset falls in the cluster of completely round smooth galaxy, and manual inspection also identifies out the outlier as a completely round smooth galaxy. These findings will facilitate the study of galaxy morphology.

[257] arXiv:1807.05639v1 [pdf, vox]

Calibrating magnification bias for the $E_G$ statistic to test general relativity

Shengqi Yang, Anthony R. Pullen
Submitted Monday 16 July 2018 @ 00:13:24 GMT
15 pages, 32 figures

We assess the effect of magnification bias on the $E_G$ statistic for probing gravity. $E_G$, a statistic constructed from power spectrum estimates of both weak lensing and redshift space distortions (RSD), directly tests general relativity (GR) while in principle being independent of clustering bias. This property has motivated its recent use in multiple tests of GR. Recent work has suggested that the magnification bias of galaxies due to foreground matter perturbations breaks the bias-independence of the $E_G$ statistic. The magnitude of this effect is very sensitive to the clustering and magnification biases of the galaxy sample. We show that for realistic values of the clustering and magnification biases, the effect for magnification bias is small relative to statistical errors for most spectroscopic galaxy surveys but large for photometric galaxy surveys. For the cases with significant magnification bias, we propose a method to calibrate magnification bias using measurements of the lensing auto-power spectrum. We test this calibration method using simulations, finding that our calibration method can calibrate $E_G$ from 2-4 times the simulation error to well within the errors, although its accuracy is sensitive to the precision of the measured redshift distribution and magnification bias, but not the clustering bias. This work gives strong evidence that this method will work increasingly well in future CMB lensing surveys.

Submitted Sun, 15 Jul 2018

[258] arXiv:1807.05621v1 [pdf, vox]

Constraints on neutrino speed, weak equivalence principle violation, Lorentz invariance violation, and dual lensing from the first high-energy astrophysical neutrino source TXS 0506+056

Ranjan Laha
Submitted Sunday 15 July 2018 @ 21:54:49 GMT
v1: 5 pages, 1 table. Comments welcome

We derive some of the most stringent constraints on neutrino speed, weak equivalence principle violation, Lorentz invariance violation, and dual lensing from the first high-energy astrophysical neutrino source: TXS 0506+056. Observation of neutrino (IceCube-170922A) and photons in a similar time frame and from the same direction is used to derive these limits. All of these constraints are stronger than those obtained from the observation of SN 1987A. We describe ways in which these constraints can be further improved by orders of magnitude.

[259] arXiv:1807.05566v1 [pdf, vox]

SHARP - V. Modelling gravitationally-lens​ed radio arcs imaged with global VLBI observations

C. Spingola, J. P. McKean, M. W. Auger, C. D. Fassnacht, L. V. E. Koopmans, D. J. Lagattuta, S. Vegetti
Submitted Sunday 15 July 2018 @ 15:39:56 GMT
15 pages, 8 figures; published by MNRAS

We present milliarcsecond (mas) angular resolution observations of the gravitationally lensed radio source MG J0751+2716 (at z=3.2) obtained with global Very Long Baseline Interferometry (VLBI) at 1.65 GHz. The background object is highly resolved in the tangential and radial directions, showing evidence of both compact and extended structure across several gravitational arcs that are 200 to 600~mas in size. By identifying compact sub-components in the multiple images, we constrain the mass distribution of the foreground z=0.35 gravitational lens using analytic models for the main deflector [power-law elliptical mass model; $\rho(r) \propto r^{-\gamma}$, where $\gamma=2$ corresponds to isothermal] and for the members of the galaxy group. Moreover, our mass models with and without the group find an inner mass-density slope steeper than isothermal for the main lensing galaxy, with $\gamma_1 = 2.08 \pm 0.02$ and $\gamma_2 = 2.16 \pm 0.02$ at the 4.2$\sigma$ level and 6.8$\sigma$ level, respectively, at the Einstein radius ($b_1 = 0.4025 \pm 0.0008$ and $b_2 = 0.307 \pm 0.002$ arcsec, respectively). We find randomly distributed image position residuals of about 3 mas, which are much larger that the measurement errors ($40$ $\mu$as on average). This suggests that at the mas level, the assumption of a smooth mass distribution fails, requiring additional structure in the model. However, given the environment of the lensing galaxy, it is not clear whether this extra mass is in the form of sub-haloes within the lens or along the line of sight, or from a more complex halo for the galaxy group.

[260] arXiv:1807.05542v1 [pdf, vox]

Simulating non-axisymmetric flows in disc galaxies

T. H. Randriamampandry, N. Deg, C. Carignan, L. M. Widrow
Submitted Sunday 15 July 2018 @ 13:19:11 GMT
19 pages, 15 figures, 5 tables, accepted for publication in A&A

We present a two-step method to simulate and study non-circular motions in strongly barred galaxies. The first step is to constrain the initial parameters using a Bayesian analysis of each galaxy's azimuthally averaged rotation curve, the 3.6 $\rm \mu m$ surface brightness, and the gas surface density. The second step is to generate equilibrium models using the GalactICS code and evolve them via GADGET-2. The bar strengths and mock velocity maps of the resulting snapshots are compared to observations in order to determine the best representation of the galaxy. We test our method on the unbarred galaxy NGC 3621 and the barred galaxies NGC 1300 and NGC 1530. NGC 3621 provides a validation of our method of generating initial conditions. NGC 1530 has an intermediate bar orientation that allows for a comparison to DiskFit. Finally NGC 1300 has a bar oriented parallel to the galaxy's major axis, where other algorithms tend to fail. Our models for NGC 3621 and NGC 1530 are comparable to those obtained using commonly available algorithms. Moreover, we have produced one of the first mass distribution models for NGC 1300.

[261] arXiv:1807.05541v1 [pdf, vox]

Can Conformal and Disformal Couplings Between Dark Sectors Explain the EDGES 21cm Anomaly?

Lin-Feng Xiao, Rui An, Le Zhang, Bin Yue, Yidong Xu, Bin Wang
Submitted Sunday 15 July 2018 @ 13:09:09 GMT
9 pages, 8 figures

The recently announced result by EDGES points an unexpected excess in the 21 cm global brightness temperature from cosmic dawn at $z\sim 17$, potentially indicating new phenomena beyond the $\Lambda$CDM model. A generic cosmological model which allows conformal and disformal couplings between dark matter and dark energy is employed to investigate the impact on the 21cm absorption signal and understand the EDGES anomaly. After exploring a wide range of parameter space for couplings, we find that the coupling effects can lead to a moderate change in the Hubble parameter while a negligible change in the spin temperature in the early Universe. Consequently, the decrease of the Hubble parameter from the mixed conformal and disformal couplings can reproduce the 21cm absorption approximately in consistent with the EDGES result at $z=17.5$. However, there is still tension in corresponding parameter space between EDGES and other cosmological observations for this model.

[262] arXiv:1807.05531v1 [pdf, vox]

Proper Motions of Sunspots' Umbral Dots at High Temporal and Spatial Resolution

Hadis Goodarzi, Serge Koutchmy, Ali Adjabshirizadeh
Submitted Sunday 15 July 2018 @ 11:52:32 GMT

To deepen the analysis of the photometric properties of the umbra of a sunspot, we study proper motions of small features such as umbral dots (UDs) inside a single sunspot observed by the Solar Optical Telescope of Hinode close to the disk center. We consider horizontal flows with high precision and details to study the transient motion behavior of UDs in short time intervals. Blue continuum images were first deconvolved with the point-spread function, such that the stray light is precisely removed and the original resolution is improved. Several images were co-added to improve the signal-to-noise ratio, keeping a reasonable temporal resolution and checking that the results are reproducible. The Fourier local correlation tracking technique is applied to the new corrected time sequence of images, and horizontal velocity maps were obtained both for the whole umbra and for a high-resolution small region of the umbra to study the smallest details of the velocity fields. We used two different Gaussian tracking windows (0.8arcsec and 0.2arcsec), which reveals two types of horizontal motions for umbral features. First, a global inner penumbra and peripheral umbra inward motion directed to the central parts is revealed as an overall proper motion of bright peripheral fine structures. Second, motions matching small cells inside the darkest parts of the umbra with apparent sink and source areas are revealed, suggesting possible upflows and downflows appearing in different bright and dark locations without a definite answer regarding their brightness identification with a convective or a buoyant cell.

[263] arXiv:1807.05530v1 [pdf, vox]

Cross-correlations between scalar perturbations and magnetic fields in bouncing universes

Debika Chowdhury, L. Sriramkumar, Marc Kamionkowski
Submitted Sunday 15 July 2018 @ 11:39:22 GMT
29 pages, 3 figures

Bouncing scenarios offer an alternative to the inflationary paradigm for the generation of perturbations in the early universe. Recently, there has been a surge in interest in examining the issue of primordial magnetogenesis in the context of bouncing universes. As in the case of inflation, the conformal invariance of the electromagnetic action needs to be broken in bouncing scenarios in order to generate primordial magnetic fields which correspond to observed strengths today. The non-minimal coupling, which typically depends on a scalar field that possibly drives the homogeneous background, leads to a cross-correlation at the level of the three-point function between the perturbation in the scalar field and the magnetic fields. This has been studied in some detail in the context of inflation and, specifically, it has been established that the three-point function satisfies the so-called consistency relation in the squeezed limit. In this work, we study the cross-correlation between the magnetic fields and the perturbation in an auxiliary scalar field in a certain class of bouncing scenarios. We consider couplings that lead to scale invariant spectra of the magnetic field and evaluate the corresponding cross-correlation between the magnetic field and the perturbation in the scalar field. We find that, when compared to de Sitter inflation, the dimensionless non-Gaussianity parameter that characterizes the amplitude of the cross-correlations proves to be considerably larger in bouncing scenarios. We also show that the aforementioned consistency condition governing the cross-correlation is violated in the bouncing models. We discuss the implications of our results.

[264] arXiv:1807.05528v1 [pdf, vox]

IDSAC - IUCAA Digital Sampler Array Controller

Sabyasachi Chattopadhyay, Pravin Chordia, A. N. Ramaprakash, Mahesh P. Burse, Bhushan Joshi, Kalpesh Chillal
Submitted Sunday 15 July 2018 @ 11:05:36 GMT
7 pages, 8 figures

IUCAA Digital Sampling Array Controller (IDSAC) is a generic CCD Controller which is flexible and powerful enough to control a wide variety of CCDs and CMOS detectors used for ground-based astronomy. It has a fully scalable architecture, which can control multiple CCDs and can be easily expanded. The controller has a modular backplane architecture consists of Single Board Controller Cards (SBCs) and can control a mosaic or independent of 5 CCDs. Key features of IDSAC contains usage of FPGA as a reconfigurable master controller, implementation of Digital CDS to achieve low noise and ability to process upto four CCD output at 1Mpixels/Sec/Channel with 16-bit resolution. The best feature of IDSAC is it uses the technique of Digital Correlated Double Sampling(DCDS). It is known that CCD video output is dominated by thermal KTC noise contributed from the summing well capacitor of the CCD output circuitry. To eliminate thermal KTC noise Correlated Double Sampling (CDS) is a very standard technique. CDS performed in Digital domain (DCDS) has several advantages over its analog counterpart, such as - less electronics, faster readout and easier post processing. It is also flexible with sampling rate and pixel throughput while maintaining the core circuit topology intact. The noise characterization of the IDSAC CDS signal chain has been performed by analytical modelling, software simulation and practical measurements. Various types of noise such as white, pink, power supply, bias etc. has been considered while creating a analytical noise model tool to predict noise of a controller system like IDSAC. Standard test bench softwares like Pspice and Multisim are used to simulate the noise performance while several tests are performed to measure the actual noise of IDSAC.The theoretical calculation matches very well with component level simulation as well as practical measurements within 10% accuracy.

[265] arXiv:1807.05522v1 [pdf, vox]

Constraints on interacting dark energy models from SDSS galaxy-galaxy weak lensing measurements

Jiajun Zhang, Rui An, Wentao Luo, Zhaozhou Li, Shihong Liao, Bin Wang
Submitted Sunday 15 July 2018 @ 10:22:57 GMT
6 pages, 3 figures

We develop a fully self-consistent N-body simulation pipeline and apply this pipeline to refine general phenomenological interacting dark energy models. Comparing our simulation results with the SDSS galaxy-galaxy weak lensing measurements, we obtain up to $820\%$ improvement of the constraint on the interaction strength compared with the previous linear examination. This improvement attributes to the correct treatment of the non-linear structure formation at low redshifts, where weak lensing measurements are sensitive.

[266] arXiv:1807.05521v1 [pdf, vox]

Probing primordial features with the primary CMB

Mario Ballardini
Submitted Sunday 15 July 2018 @ 10:14:14 GMT
6 pages, 2 figures, 1 table

CMB photons travel from the last scattering surface, when the primary CMB has been generated, along the surface of the light cone to us. During their travel, they are affected by many secondary effects such as the integrated Sachs-Wolfe effect and CMB lensing. These CMB secondary effects modify the CMB primary power spectrum adding degeneracies and decreasing the sensibility to primordial parameters. The possibility to reconstruct the primary CMB anisotropies will allow us to have a more direct observable to test the physics of the early universe. We propose to study the imprint of features in the primordial power spectrum with the primary CMB after the subtraction of the reconstructed ISW signal from the observed CMB temperature angular power spectrum. We consider the application to features models able to fit two of the large scales anomalies observed in the CMB temperature angular power spectrum: the deficit of power at $\ell \sim 2$ and at $\ell \sim 22$. This method allows to improve significantly the constraints on the features parameters up to $16\%$ for models predicting a suppression of power of the quadrupole and up to $27\%$ for models with features at $\ell \sim 22$, assuming instrumental sensitivity similar to the $Planck$ satellite (depending on the goodness of the ISW reconstruction). Furthermore, it gives the opportunity to understand if these anomalies are attributed to early- or late-time physics.

[267] arXiv:1807.05494v1 [pdf, vox]

Role of Cosmic Ray Streaming and Turbulent Damping in Driving Galactic Winds

F. Holguin, M. Ruszkowski, A. Lazarian, R. Farber, H. -Y. K. Yang
Submitted Sunday 15 July 2018 @ 05:54:10 GMT
11 pages, 5 figures

Large-scale galactic winds driven by stellar feedback are one phenomenon that influences the dynamical and chemical evolution of a galaxy, redistributing material throughout the circumgalatic medium. Non-thermal feedback from galactic cosmic rays (CRs) -high-energy charged particles accelerated in supernovae and young stars - can impact the efficiency of wind driving. The streaming instability limits the speed at which they can escape. However, in the presence of turbulence, the streaming instability is subject to suppression that depends on the magnetization of turbulence given by its Alfv\'en Mach number. While previous simulations that relied on a simplified model of CR transport have shown that super-Alfv\'enic streaming of CRs enhances galactic winds, in the present paper we take into account a realistic model of streaming suppression. We perform three-dimensional magnetohydrodynamic simulations of a section of a galactic disk and find that turbulent damping dependent on local magnetization of turbulent interstellar medium (ISM) leads to more spatially extended gas and CR distributions compared to the earlier streaming calculations, and that scale-heights of these distributions increase for stronger turbulence. Our results indicate that the star formation rate increases with the level of turbulence in the ISM. We also find that the instantaneous wind mass loading is sensitive to local streaming physics with the mass loading dropping significantly as the strength of turbulence increases.

[268] arXiv:1807.05488v1 [pdf, vox]

Numerical study of active galactic nucleus feedback in an elliptical galaxy with {\it MACER}

Feng Yuan, Jeremiah P. Ostriker, DooSoo Yoon, Ya-Ping Li, Luca Ciotti, Zhao-Ming Gan, Luis C. Ho, Fulai Guo
Submitted Sunday 15 July 2018 @ 04:57:39 GMT
7 pages, 3 figures; proceedings of the IAUS342 "Perseus in Sicily: from black hole to cluster outskirts"

This paper summarizes our recent works of studying AGN feedback in an isolated elliptical galaxy by performing high-resolution hydrodynamical numerical simulations. Bondi radius is resolved and the mass accretion rate of the black hole is calculated. The most updated AGN physics, namely the discrimination of cold and hot accretion modes and the exact descriptions of the AGN radiation and wind for a given accretion rate are adopted and their interaction with the gas in the host galaxy is calculated. Physical processes such as star formation and SNe feedback are taken into account. Consistent with observation, we find the AGN spends most of the time in the low-luminosity regime. AGN feedback overall suppresses the star formation; but depending on location in the galaxy and time, it can also enhance it. The light curve of specific star formation rate is not synchronous with the AGN light curve. We find that wind usually plays a dominant role in controlling the AGN luminosity and star formation, but radiation also cannot be neglected.

[269] arXiv:1807.05480v1 [pdf, vox]

Depletion of 15N in the center of L1544: Early transition from atomic to molecular nitrogen?

Kenji Furuya, Yoshimasa Watanabe, Takeshi Sakai, Yuri Aikawa, Satoshi Yamamoto
Submitted Sunday 15 July 2018 @ 02:51:27 GMT
5 pages, 2 figures, 2 tables, Accepted for publication in A&A Letters

We performed sensitive observations of the N15ND+(1-0) and 15NND+(1-0) lines toward the prestellar core L1544 using the IRAM 30m telescope. The lines are not detected down to 3 sigma levels in 0.2 km/s channels of around 6 mK. The non-detection provides the lower limit of the 14N/15N ratio for N2D+ of ~700-800, which is much higher than the elemental abundance ratio in the local ISM of ~200-300. The result indicates that N2 is depleted in 15N in the central part of L1544, because N2D+ preferentially traces the cold dense gas, and because it is a daughter molecule of N2. In-situ chemistry is unlikely responsible for the 15N depletion in N2; neither low-temperature gas phase chemistry nor isotope selective photodissociation of N2 explains the 15N depletion; the former prefers transferring 15N to N2, while the latter requires the penetration of interstellar FUV photons into the core center. The most likely explanation is that 15N is preferentially partitioned into ices compared to 14N via the combination of isotope selective photodissociation of N2 and grain surface chemistry in the parent cloud of L1544 or in the outer regions of L1544 which are not fully shielded from the interstellar FUV radiation. The mechanism is the most efficient at the chemical transition from atomic to molecular nitrogen. In other words, our result suggests that the gas in the central part of L1544 already went trough the transition from atomic to molecular nitrogen in the earlier evolutionary stage, and that N2 is currently the primary form of gas-phase nitrogen.

[270] arXiv:1807.05479v1 [pdf, vox]

The timestep constraint in solving the gravitational wave equations sourced by hydromagnetic turbulence

A. Roper Pol, A. Brandenburg, T. Kahniashvili, A. Kosowsky, S. Mandal
Submitted Sunday 15 July 2018 @ 02:39:50 GMT
14 pages, 6 figures. Submitted to GAFD, special edition on "Physics and Algorithms of the Pencil Code"

Hydromagnetic turbulence produced during phase transitions in the early universe can be a powerful source of stochastic gravitational waves (GWs). GWs can be modeled by the linearized spatial part of the Einstein equations sourced by the Reynolds and Maxwell stresses. We have implemented a GW solver into the {\sc Pencil Code}, which uses a third order timestep and sixth order finite differences. We study the appearance of a numerical degradation of the GW amplitude at the highest wavenumbers, which depends on the length of the timestep---even when the Courant-Friedrichs-L​ewy condition is ten times below the stability limit. This degradation leads to a numerical error, which is found to scale with the third power of the timestep. A similar degradation is not seen in the magnetic and velocity fields. Yet, we argue that such degradation could also occur in those fields, but it is being masked by the forward cascade of energy, which populates all higher wavenumbers in a timestep-independent fashion. A similar process is not possible for the GWs, because their evolution equations are linear.

Submitted Sat, 14 Jul 2018

[271] arXiv:1807.05449v1 [pdf, vox]

Differentially rotating neutron stars in scalar-tensor theories of gravity

Daniela D. Doneva, Stoytcho S. Yazadjiev, Nikolaos Stergioulas, Kostas D. Kokkotas
Submitted Saturday 14 July 2018 @ 21:17:38 GMT
8 pages, 4 figures

We present the first numerical models of differentially rotating stars in alternative theories of gravity. We chose a particular class of scalar-tensor theories of gravity that is indistinguishable from GR in the weak field regime but can lead to significant deviations when strong fields are considered. We show that the maximum mass that a differentially rotating neutron star can sustain increases significantly for scalarized solutions and such stars can reach larger angular momenta. In addition, the presence of a nontrivial scalar field has the effect of increasing the required axis ratio for reaching a given value of angular momentum, when compared to a corresponding model of same rest mass in general relativity. We find that the scalar field also makes rapidly rotating models less quasi-toroidal than their general-relativistic counterparts. For large values of the angular momentum and values of the coupling parameter that are in agreement with the observations, we find a second turning point for scalarized models along constant angular momentum sequences, which could have interesting implications for the stability of remnants created in a binary neutron star merger.

[272] arXiv:1807.05445v1 [pdf, vox]

A note on Inflation and the Swampland

Alex Kehagias, Antonio Riotto
Submitted Saturday 14 July 2018 @ 20:58:06 GMT
5 pages

We provide some comments about the constraints on the inflationary models inferred from the two Swampland criteria which have been recently proposed. In particular we argue that, in the absence of any knowledge about the origin of the adiabatic curvature perturbations, within the slow-roll single field models of inflation there is no tension between the swampland criteria and the current lower bound on the tensor-to-scalar ratio.

[273] arXiv:1807.05441v1 [pdf, vox]

Towards building a first northern-sky sample of 'Extremely Inverted Spectrum Extragalactic Radio Sources (EISERS)'

Mukul Mhaskey, Gopal-Krishna, Surajit Paul
Submitted Saturday 14 July 2018 @ 20:54:37 GMT

We present here an extension of our search for EISERS (Extremely Inverted Spectrum Extragalactic Radio Sources) to the northern hemisphere. With an inverted radio spectrum of slope $\alpha$ $>$ + 2.5, these rare sources would either require a non-standard particle acceleration mechanism (in the framework of synchrotron self-absorption hypothesis), or a severe free-free absorption which attenuates practically all of their synchrotron radiation at metre wavelengths. A list of 15 EISERS candidates is presented here. It was assembled by applying a sequence of selection filters, starting with the two available large-sky radio surveys, namely the WENSS (325 MHz) and the ADR-TGSS (150 MHz). These surveys offer the twin advantages of being fairly deep (typical rms $<$ 10 mJy/beam) and having a sub-arcminute resolution. Their zone of overlap spreads over 1.3$\pi$ steradian in the northern hemisphere. Radio spectra are presented for the entire sample of 15 EISERS candidates, of which 8 spectra are of GPS type. Eleven members of the sample are associated with previously known quasars. Information on the parsec-scale radio structure, available for several of these sources, is also summarized.

[274] arXiv:1807.05435v1 [pdf, vox]

Reionization in the dark and the light from Cosmic Microwave Background

Dhiraj Kumar Hazra, Daniela Paoletti, Fabio Finelli, George F. Smoot
Submitted Saturday 14 July 2018 @ 19:52:50 GMT
16 pages, 9 figures and 1 table

We explore the constraints on the history of reionization from Planck 2015 Cosmic Microwave Background (CMB) data and we derive the forecasts for future CMB observations. We consider a class of monotonic histories of reionization as parametrized by two additional extra parameters with respect to the average optical depth used in the instantaneous reionization modeling. We investigate the degeneracies between the history of reionization and selected extensions of the standard cosmological model. In particular, we consider the degeneracies with the total mass of the neutrino sector and we discuss the possible correlation between the dark matter annihilation and the duration of reionization in the CMB. We use an extension to poly-reion model that was proposed in Hazra and Smoot, JCAP 1711, 028 (2017). We compare the constraints from Planck 2015 data with the predicted constraints from possible future CMB mission as LiteBIRD, and we also use the proposed CORE-like specifications as an example of what higher resolution can bring in addition. We find that the degeneracy between the average optical depth and the duration of reionization will be substantially removed by both concepts. Degeneracies between the reionization history and either the total neutrino mass and properties of dark matter annihilation will also be improved by future surveys. We find only marginal improvement in the constraints on reionization history for the higher resolution in the case of long duration of reionization.

[275] arXiv:1807.05434v1 [pdf, vox]

A highly magnified gravitationally lensed red quasar at z = 2.5 with significant flux anomaly: Uncovering a missing population

E. Glikman, C. E. Rusu, S. G. Djorgovski, M. J. Graham, D. Stern, T. Urrutia, M. Lacy, J. M. O'Meara
Submitted Saturday 14 July 2018 @ 19:34:35 GMT
Submitted to the Astrophysical Journal. 15 pages, 8 Figures, 6 tables

We present the discovery of a gravitationally lensed dust-reddened QSO at $z=2.517$ discovered in a survey for red QSOs by infrared selection. $Hubble~Space~Telesc​ope$ imaging in the WFC3/IR F160W and F125W filters reveals a quadruply lensed system in a cusp configuration. We find that compared to the central image of the cusp, the nearby, brightest image is anomalous by a factor of $\sim7-11$. Although the source is extremely bright in the mid-infrared, a magnification by a factor of $\sim50-120$ places an upper limit of 1.35 mJy on the intrinsic mid-infrared brightness, well below the $WISE~W4$ detection limit of 6 mJy. We find that this QSO is moderately reddened, with $E(B-V)=0.7$ and that $\sim1\%$ of the intrinsic spectrum is leaked back into the line of sight resulting in an upturn in its UV spectrum. We conclude that the QSO's reddening is intrinsic and not due to the lens. Consistent with previous red quasar samples, this source exhibits outflows in its spectrum as well as morphological properties suggestive of it being in a merger-driven transitional phase. Depending on how $L_{\rm bol}$ is computed, the quasar's accretion rate may be as high as $0.26~L_{\rm Edd}$. We detect two Lyman limit systems, at $z=2.102$ and $z=2.431$, with absorption by metal lines likely at small impact parameter to the QSO, and a putative lens redshift of $z=0.599$. Given the rarity of quad lenses, the discovery of this source allows detailed study of a less luminous, more typical infrared-selected quasar at high redshift.

[276] arXiv:1807.05422v1 [pdf, vox]

WFIRST Coronagraph Technology Requirements: Status Update and Systems Engineering Approach

Ewan S. Douglas, Ashley K. Carlton, Kerri L. Cahoy, N. Jeremy Kasdin, Margaret Turnbull, Bruce Macintosh
Submitted Saturday 14 July 2018 @ 16:58:41 GMT
16 pages, 4 figures

The coronagraphic instrument (CGI) on the Wide-Field Infrared Survey Telescope (WFIRST) will demonstrate technologies and methods for high-contrast direct imaging and spectroscopy of exoplanet systems in reflected light, including polarimetry of circumstellar disks. The WFIRST management and CGI engineering and science investigation teams have developed requirements for the instrument, motivated by the objectives and technology development needs of potential future flagship exoplanet characterization missions such as the NASA Habitable Exoplanet Imaging Mission (HabEx) and the Large UV/Optical/IR Surveyor (LUVOIR). The requirements have been refined to support recommendations from the WFIRST Independent External Technical/Management​/Cost Review (WIETR) that the WFIRST CGI be classified as a technology demonstration instrument instead of a science instrument. This paper provides a description of how the CGI requirements flow from the top of the overall WFIRST mission structure through the Level 2 requirements, where the focus here is on capturing the detailed context and rationales for the CGI Level 2 requirements. The WFIRST requirements flow starts with the top Program Level Requirements Appendix (PLRA), which contains both high-level mission objectives as well as the CGI-specific baseline technical and data requirements (BTR and BDR, respectively)... We also present the process and collaborative tools used in the L2 requirements development and management, including the collection and organization of science inputs, an open-source approach to managing the requirements database, and automating documentation. The tools created for the CGI L2 requirements have the potential to improve the design and planning of other projects, streamlining requirement management and maintenance. [Abstract Abbreviated]

[277] arXiv:1807.05373v1 [pdf, vox]

The Low Detection Rate of Pair Instability Supernovae and the Effect of the Core Carbon Fraction

Koh Takahashi
Submitted Saturday 14 July 2018 @ 10:32:04 GMT
14 pages, 11 figures. Accepted for publication in ApJ

The pair instability supernova (PISN) is a common fate of very massive stars (VMSs). Current theory predicts the initial and the CO core mass ranges for PISNe of $\sim$140-260 $M_\odot$ and $\sim$65-120 $M_\odot$ respectively for stars that are not much affected by the wind mass loss. The corresponding relative event rate between PISNe and core collapse supernovae is estimated to be $\sim$1% for the present-day initial mass function. However, no confident PISN candidate has been detected so far, despite more than 1,000 supernovae are discovered every recent years. We investigate the evolution of VMSs with various core carbon-to-oxygen ratios for the first time, by introducing a multiplication factor $f_{\rm cag} \in [ 0.1, 1.2 ]$ to the $^{12}$C($\alpha, \gamma$)$^{16}$O reaction rate. We find that a less massive VMS with a high $X$(C)/$X$(O) develops shell convection during the core carbon-burning phase, with which the star avoids the pair-creation instability. The second result is the high explodability for a massive VMS, i.e., a star with high $X$(C)/$X$(O) explodes with a smaller explosion energy. Consequently, the initial and the CO core mass ranges for PISNe are significantly increased. Finally, a PISN with high $X$(C)/$X$(O) yields smaller amount of $^{56}$Ni. Therefore, PISNe with high $X$(C)/$X$(O) are much rarer and fainter to be detected. This result advances the first theory to decrease the PISN event rate by directly shifting the CO core mass range.

[278] arXiv:1807.05369v1 [pdf, vox]

K2 Photometry of RR Lyrae Stars

E. Plachy, L. Molnár, A. Bódi, M. Skarka, Á. L. Juhász, Á. Sódor, P. Klagyivik, R. Szabó
Submitted Saturday 14 July 2018 @ 09:48:41 GMT
5 pages, 3 figures, to be published in the proceedings of "The RR Lyrae 2017 Conference", Niepolomice, Poland, 17-21 September 2017

Thousands of RR Lyrae stars have been observed by the \textit{Kepler} space telescope so far. We developed a photometric pipeline tailored to the light variations of these stars, called the Extended Aperture Photometry (EAP). We present the comparison of our photometric solutions for Campaigns 0 through 6 with the other pipelines available, e.g., SAP/PDCSAP, K2P2, EVEREST, and others. We focus on the problems caused by instrumental effects and the detectability of the low-amplitude additional modes.

[279] arXiv:1807.05336v1 [pdf, vox]

ALMA observations of the very young Class 0 protostellar system HH 211-mms: a 30-au dusty disk with a disk-wind traced by SO?

Chin-Fei Lee, Zhi-Yun Li, Naomi Hirano, Hsien Shang, Paul T. P. Ho, Qizhou Zhang
Submitted Saturday 14 July 2018 @ 06:13:15 GMT
20 pags, 6 figures

HH 211-mms is one of the youngest Class 0 protostellar systems in Perseus at ~ 235 pc away. We have mapped its central region at up to ~ 7 AU (0.03") resolution. A dusty disk is seen deeply embedded in a flattened envelope, with an intensity jump in dust continuum at ~ 350 GHz. It is nearly edge-on and is almost exactly perpendicular to the jet axis. It has a size of ~ 30 au along the major axis. It is geometrically thick, indicating that the (sub)millimeter light emitting grains have yet to settle to the midplane. Its inner part is expected to have transformed into a Keplerian rotating disk with a radius of ~ 10 au. A rotating disk atmosphere and a compact rotating bipolar outflow are detected in SO. The outflow fans out from the inner disk surfaces and is rotating in the same direction as the flattened envelope, and hence could trace a disk wind carrying away angular momentum from the inner disk. From the rotation of the disk atmosphere, the protostellar mass is estimated to be <~ 50 M_Jup. Together with results from the literature, our result favors a model where the disk radius grows linearly with the protostellar mass, as predicted by models of pre-stellar dense core evolution that asymptotes to an $r^{-1}$ radial profile for both the column density and angular velocity.

[280] arXiv:1807.05334v1 [pdf, vox]

Condition for low-mass star formation in shock-compressed metal-poor clouds

Daisuke Nakauchi, Kazuyuki Omukai, Raffaella Schneider
Submitted Saturday 14 July 2018 @ 05:33:50 GMT
15 pages, 8 figures, accepted for publication in MNRAS

Shocks may have been prevalent in the early Universe, associated with virialization and supernova explosions, etc. Here, we study thermal evolution and fragmentation of shock-compressed clouds, by using a one-zone model with detailed thermal and chemical processes. We explore a large range of initial density (1-1e5 /cm^3), metallicity (0-1e-2 Z_sun), UV strength (0-500 times Galactic value), and cosmic microwave background temperature (10 and 30 K). Shock-compressed clouds contract isobarically via atomic and molecular line cooling, until self-gravitating clumps are formed by fragmentation. If the metals are only in the gas-phase, the clump mass is higher than ~ 3 M_sun in any conditions we studied. Although in some cases with a metallicity higher than ~ 1e-3 Z_sun, re-fragmentation of a clump is caused by metal-line cooling, this fragment mass is higher than ~ 30 M_sun. On the other hand, if about half the mass of metals is condensed in dust grains, as in the Galactic interstellar medium, dust cooling triggers re-fragmentation of a clump into sub-solar mass pieces, for metallicities higher than ~ 1e-5 Z_sun. Therefore, the presence of dust is essential in low-mass (< M_sun) star formation from a shock-compressed cloud.

[281] arXiv:1807.05312v1 [pdf, vox]

Comparing Redundant and Sky Model Based Interferometric Calibration: A First Look with Phase II of the MWA

W. Li, J. C. Pober, B. J. Hazelton, N. Barry, M. F. Morales, I. Sullivan, A. R. Parsons, Z. S. Ali, J. S. Dillon, A. P. Beardsley, J. D. Bowman, F. Briggs, R. Byrne, P. Carroll, B. Crosse, D. Emrich, A. Ewall-Wice, L. Feng, T. M. O. Franzen, J. N. Hewitt, L. Horsley, D. C. Jacobs, M. Johnston-Hollitt, C. Jordan, R. C. Joseph, D. L. Kaplan, D. Kenney, H. Kim, P. Kittiwisit, A. Lanman, J. Line, B. McKinley, D. A. Mitchell, S. Murray, A. Neben, A. R. Offringa, D. Pallot, S. Paul, B. Pindor, P. Procopio, M. Rahimi, J. Riding, S. K. Sethi, N. Udaya Shankar, K. Steele, R. Subrahmanian, M. Tegmark, N. Thyagarajan, S. J. Tingay, C. Trott, M. Walker, R. B. Wayth, R. L. Webster, A. Williams, C. Wu, S. Wyithe
Submitted Saturday 14 July 2018 @ 00:19:16 GMT
20 pages, 11 figures. Accepted to ApJ

Interferometric arrays seeking to measure the 21 cm signal from the Epoch of Reionization must contend with overwhelmingly bright emission from foreground sources. Accurate recovery of the 21 cm signal will require precise calibration of the array, and several new avenues for calibration have been pursued in recent years, including methods using redundancy in the antenna configuration. The newly upgraded Phase II of Murchison Widefield Array (MWA) is the first interferometer that has large numbers of redundant baselines while retaining good instantaneous UV-coverage. This array therefore provides a unique opportunity to compare redundant calibration with sky-model based algorithms. In this paper, we present the first results from comparing both calibration approaches with MWA Phase II observations. For redundant calibration, we use the package OMNICAL, and produce sky-based calibration solutions with the analysis package Fast Holographic Deconvolution (FHD). There are three principal results. (1) We report the success of OMNICAL on observations of ORBComm satellites, showing substantial agreement between redundant visibility measurements after calibration. (2) We directly compare OMNICAL calibration solutions with those from FHD, and demonstrate these two different calibration schemes give extremely similar results. (3) We explore improved calibration by combining OMNICAL and FHD. We evaluate these combined methods using power spectrum techniques developed for EoR analysis and find evidence for marginal improvements mitigating artifacts in the power spectrum. These results are likely limited by signal-to-noise in the six hours of data used, but suggest future directions for combining these two calibration schemes.

[282] arXiv:1807.05310v1 [pdf, vox]

Data-constrained Model for Coronal Mass Ejections Using Graduated Cylindrical Shell Method

Talwinder Singh, Mehmet Sarp Yalim, Nikolai V Pogorelov
Submitted Saturday 14 July 2018 @ 00:07:40 GMT

Coronal Mass Ejections (CMEs) are major drivers of extreme space weather conditions, this being a matter of serious concern for our modern technologically-depe​ndent society. Development of numerical approaches that would simulate CME generation and propagation through the interplanetary space is an important step towards our capability to predict CME arrival times at Earth and their geo-effectiveness. In this paper, we utilize a data-constrained Gibson--Low (GL) flux rope model to generate CMEs. We derive the geometry of the initial GL flux rope using the Graduated Cylindrical Shell (GCS) method. This method uses multiple viewpoints from STEREO A & B Cor1/Cor2, and SOHO/LASCO C2/C3 coronagraphs to determine the size and orientation of a CME flux rope as it starts to erupt from the Sun. A flux rope generated in this way is inserted into a quasi-steady global magnetohydrodynamics (MHD) background solar wind flow driven by SDO/HMI line-of-sight magnetogram data, and erupts immediately. Numerical results obtained with the Multi-Scale Fluid-Kinetic Simulation Suite (MS-FLUKSS) code are compared with STEREO and SOHO/LASCO coronagraph observations in particular in terms of the CME speed, acceleration, and magnetic field structure.

[283] arXiv:1807.05309v1 [pdf, vox]

No Strong Geometric Beaming in the Ultraluminous Neutron Star Binary NGC 300 ULX-1 (SN 2010da) from Swift and Gemini

Breanna A. Binder, Emily M. Levesque, Trevor Dorn-Wallenstein
Submitted Saturday 14 July 2018 @ 00:05:00 GMT
Accepted to AAS Journals. 9 pages, 5 figures

We have obtained near-simultaneous Swift/XRT imaging and Gemini GMOS spectroscopy for the ultraluminous X-ray source (ULX) NGC~300 ULX-1 (formerly designated SN~2010da). The observed X-ray emission is consistent with an inhomogeneous wind that partially obscures a central, bright inner accretion disk. We simultaneously fit eleven 0.3-10 keV spectra obtained over a $\sim$1 year time period (2016 April to 2017 July) using the same partial covering model, and find that although the covering fraction varies significantly (from 78% to consistent with 0%), the unabsorbed luminosity remains essentially constant across all observations ($2-6\times10^{39}$ erg s$^{-1}$). A relatively high 0.3-10 keV fractional variability amplitude ($F_{\rm var}$) of $\sim$30% is observed in all eleven observations. Optical spectra from Gemini exhibit numerous emission lines (e.g., H$\alpha$, H$\beta$, He II $\lambda$4686) which suggest that the neutron star primary is photoionizing material in the immediate vicinity of the binary. We compare the He II $\lambda$4686 line luminosity ($\sim7-9\times10^{3​5}$ erg s$^{-1}$) to the contemporaneous soft X-ray emission and find the X-ray emission is broadly consistent with the observed He II line luminosity. The combination of our X-ray observations and optical spectroscopy suggest that geometric beaming effects in the ULX-1 system are minimal, making ULX-1 one of only a few bona fide ULXs to be powered by accretion onto a neutron star.

Submitted Fri, 13 Jul 2018

[284] arXiv:1807.05305v1 [pdf, vox]

The Origin of Heavy Element Content Trend in Giant Planets via Core Accretion

Yasuhiro Hasegawa, Geoffrey Bryden, Masahiro Ikoma, Gautam Vasisht, Mark Swain
Submitted Friday 13 July 2018 @ 23:31:35 GMT
17 pages, 8 figures, 5 tables; submitted to ApJ; the revision has been made, following the referee report

We explore the origin of the trend of heavy elements in observed massive exoplanets. Coupling of better measurements of mass ($M_p$) and radius of exoplanets with planet structure models enables estimating the total heavy element mass ($M_Z$) in these planets. The corresponding relation is characterized by a power-law profile, $M_Z \propto M_p^{3/5}$. We develop a simplified, but physically motivated analysis to investigate how the power-law profile can be produced under the current picture of planet formation. Making use of the existing semi-analytical formulae of accretion rates of pebbles and planetesimals, our analysis shows that the relation can be reproduced well if it traces the final stage of planet formation. In the stage, planets accrete solids from gapped planetesimal disks and gas accretion is limited by disk evolution. We also find that dust accretion accompanying with gas accretion does not contribute to $M_Z$ for planets with $M_p < 10^3 M_{\oplus}$. Our findings are broadly consistent with that of previous studies, yet we explicitly demonstrate how planetesimal dynamics is crucial for better understanding the relation. While our approach is simple, we can also reproduce the trend of a correlation between planet metallicity and $M_p$ that is obtained by detailed population synthesis calculations, when the same assumption is adopted. Our analysis suggests that pebble accretion would not play a direct role at the final stage of planet formation, whereas radial drift of pebbles might be important indirectly for metal enrichment of planets. Detailed numerical simulations and more observational data are required for confirming our analysis.

[285] arXiv:1807.05291v1 [pdf, vox]

LASSO: Large Adaptive optics Survey for Substellar Objects using the new SAPHIRA detector on Robo-AO

Maissa Salama, James Ou, Christoph Baranec, Michael C. Liu, Brendan P. Bowler, Reed Riddle, Dmitry Duev, Donald Hall, Dani Atkinson, Sean Goebel, Mark Chun, Shane Jacobson, Charles Lockhart, Eric Warmbier, Shrinivas Kulkarni, Nicholas M. Law
Submitted Friday 13 July 2018 @ 21:55:44 GMT
10 pages, 7 figures, SPIE conference proceedings

We report on initial results from the largest infrared AO direct imaging survey searching for wide orbit (>100 AU) massive exoplanets and brown dwarfs as companions around young nearby stars using Robo-AO at the 2.1-m telescope on Kitt Peak, Arizona. The occurrence rates of these rare substellar companions are critical to furthering our understanding of the origin of planetary-mass companions on wide orbits. The observing efficiency of Robo-AO allows us to conduct a survey an order of magnitude larger than previously possible. We commissioned a low-noise high-speed SAPHIRA near-infrared camera to conduct this survey and report on its sensitivity, performance, and data reduction process.

[286] arXiv:1807.05282v1 [pdf, vox]

The High Definition X-ray Imager (HDXI) Instrument on the Lynx X-Ray Surveyor

Abraham D. Falcone, Ralph P. Kraft, Marshall W. Bautz, Jessica A. Gaskin, John A. Mulqueen, Doug A. Swartz, for the Lynx Science \& Technology Definition Team
Submitted Friday 13 July 2018 @ 21:07:32 GMT
proceedings of SPIE Astronomical Telescopes + Instrumentation (10699-37)

The Lynx X-ray Surveyor Mission is one of 4 large missions being studied by NASA Science and Technology Definition Teams as mission concepts to be evaluated by the upcoming 2020 Decadal Survey. By utilizing optics that couple fine angular resolution (<0.5 arcsec HPD) with large effective area (~2 m^2 at 1 keV), Lynx would enable exploration within a unique scientific parameter space. One of the primary soft X-ray imaging instruments being baselined for this mission concept is the High Definition X-ray Imager, HDXI. This instrument would achieve fine angular resolution imaging over a wide field of view (~ 22 x 22 arcmin, or larger) by using a finely-pixelated silicon sensor array. Silicon sensors enable large-format/small-p​ixel devices, radiation tolerant designs, and high quantum efficiency across the entire soft X-ray bandpass. To fully exploit the large collecting area of Lynx (~30x Chandra), without X-ray event pile-up, the HDXI will be capable of much faster frame rates than current X-ray imagers. The planned requirements, capabilities, and development status of the HDXI will be described.

[287] arXiv:1807.05279v1 [pdf, vox]

The True Luminosities of Planetary Nebulae in M31's Bulge: Massive Central Stars from an Old Stellar Population

Brian D. Davis, Robin Ciardullo, George H. Jacoby, John. J. Feldmeier, Briana L. Indahl
Submitted Friday 13 July 2018 @ 20:51:22 GMT
13 pages, 14 figures

We measure the Balmer decrements of 23 of the brightest planetary nebulae (PNe) in the inner bulge ($r \lesssim 3$ arcmin) of M31 and de-redden the bright end of the region's [O III] $\lambda 5007$ planetary nebula luminosity function. We show that the most luminous PNe produce $\gtrsim 1{,}200 \, \rm{L}_{\odot}$ of power in their [O III] $\lambda 5007$ line, implying central star luminosities of at least $\sim 11{,}000 \, \rm{L}_{\odot}$. Even with the most recent accelerated-evolutio​n post-AGB models, such luminosities require central star masses in excess of $0.66 \, \rm{M}_{\odot}$, and main sequence progenitors of at least $\sim 2.5 \, \rm{M}_{\odot}$. Since M31's bulge has very few intermediate-age stars, we conclude that conventional single-star evolution cannot be responsible for these extremely luminous objects. We also present the circumstellar extinctions for the region's bright PNe and demonstrate that the distribution is similar to that found for PNe in the Large Magellanic Cloud, with a median value of $A_{5007} = 0.71$. Finally, we compare our results to extinction measurements made for PNe in the E6 elliptical NGC 4697 and the interacting lenticular NGC 5128. We show that such extinctions are not unusual, and that the existence of very high-mass PN central stars is a general feature of old stellar populations. Our results suggest that single-star population synthesis models significantly underestimate the maximum luminosities and total integrated light of AGB stars.

[288] arXiv:1807.05278v1 [pdf, vox]

The James Webb Space Telescope North Ecliptic Pole Time-Domain Field -- I: Field Selection of a JWST Community Field for Time-Domain Studies

Rolf A. Jansen, Rogier A. Windhorst
Submitted Friday 13 July 2018 @ 20:49:42 GMT
PDFLaTeX, 14 pages with 7 figures (18 panels), submitted to PASP

We describe the selection of the James Webb Space Telescope (JWST) North Ecliptic Pole (NEP) Time-Domain Field (TDF), a ~14' diameter field located within JWST's northern Continuous Viewing Zone (CVZ) and centered at (RA, Dec)_J2000 = (17:22:47.896, +65:49:21.54). We demonstrate that this is the only region in the sky where JWST can observe a clean (i.e., free of bright foreground stars and with low Galactic foreground extinction) extragalactic deep survey field of this size at arbitrary cadence or at arbitrary orientation, and without a penalty in terms of a raised Zodiacal background. This will crucially enable a wide range of new and exciting time-domain science, including high redshift transient searches and monitoring (e.g., SNe), variability studies from Active Galactic Nuclei (AGN) to brown dwarf atmospheres, as well as proper motions of possibly extreme scattered Kuiper Belt and Inner Oort Cloud Objects, and of nearby Galactic brown dwarfs, low-mass stars, and ultracool white dwarfs. A JWST/NIRCam+NIRISS GTO program will provide an initial 0.8--5.0micron spectrophotometric characterization to m_AB ~ 28.8+/-0.3 mag of four orthogonal "spokes" within this field. The multi-wavelength (radio through X-ray) context of the field is in hand (ground-based near-UV--visible--ne​ar-IR), in progress (VLA 3GHz, VLBA 5GHz, HST UV--visible, Chandra X-ray, IRAM30m 1.3 and 2mm), or scheduled (JCMT 850micron). We welcome and encourage ground- and space-based follow-up of the initial GTO observations and ancillary data, to realize its potential as an ideal JWST time-domain community field.

[289] arXiv:1807.05276v1 [pdf, vox]

Robust Chauvenet Outlier Rejection

M. P. Maples, D. E. Reichart, N. C. Konz, T. A. Berger, A. S. Trotter, J. R. Martin, D. A. Dutton, M. L. Paggen, R. E. Joyner, C. P. Salemi
Submitted Friday 13 July 2018 @ 20:40:38 GMT
62 pages, 48 figures, 7 tables, accepted for publication in ApJS

Sigma clipping is commonly used in astronomy for outlier rejection, but the number of standard deviations beyond which one should clip data from a sample ultimately depends on the size of the sample. Chauvenet rejection is one of the oldest, and simplest, ways to account for this, but, like sigma clipping, depends on the sample's mean and standard deviation, neither of which are robust quantities: Both are easily contaminated by the very outliers they are being used to reject. Many, more robust measures of central tendency, and of sample deviation, exist, but each has a tradeoff with precision. Here, we demonstrate that outlier rejection can be both very robust and very precise if decreasingly robust but increasingly precise techniques are applied in sequence. To this end, we present a variation on Chauvenet rejection that we call "robust" Chauvenet rejection (RCR), which uses three decreasingly robust/increasingly precise measures of central tendency, and four decreasingly robust/increasingly precise measures of sample deviation. We show this sequential approach to be very effective for a wide variety of contaminant types, even when a significant -- even dominant -- fraction of the sample is contaminated, and especially when the contaminants are strong. Furthermore, we have developed a bulk-rejection variant, to significantly decrease computing times, and RCR can be applied both to weighted data, and when fitting parameterized models to data. We present aperture photometry in a contaminated, crowded field as an example. RCR may be used by anyone at https://skynet.unc.e​du/rcr, and source code is available there as well.

[290] arXiv:1807.05267v1 [pdf, vox]

Photosynthesis on a planet orbiting an M dwarf: enhanced effectiveness during flares

D. J. Mullan, H. P. Bais
Submitted Friday 13 July 2018 @ 19:54:50 GMT
to be published in Astronomical Journal

On planets near M dwarfs, photosynthesis (PS) will occur with an effectiveness which depends on the supply of visible photons with wavelengths between 400 and 700 nm. In this paper, we quantify the effectiveness of PS in two contexts which are relevant for M dwarfs. First, using photons from an M dwarf in its quiescent non-flaring state, we find that PS on an M dwarf planet in the HZ of its parent star is less effective than on Earth by a factor of 10 for a flare star with mid-M spectral type. For a flare star with late-M spectral type, PS effectiveness is smaller than on Earth by a factor of 100 or more. Second, using photons which are incident on the HZ planet during flares, we find that PS effectiveness can increase by factors of 5-20 above the quiescent values. In the case of a flare star with mid-M spectral type, we find that the PS effectiveness during a flare can increase up to as much as 50-60 percent of the values on Earth. However, for a late-M flare star, even during flares, the PS effectiveness remains almost one order of magnitude smaller than on Earth. We suggest that for biological processes on M dwarf planets, the stellar activity cycle may replace the orbital period as the year.

[291] arXiv:1807.05260v1 [pdf, vox]

Are NLS1s highly accreting low black hole mass AGNs?

James K. Williams, Mario Gliozzi, Ross V. Rudzinsky
Submitted Friday 13 July 2018 @ 19:36:33 GMT
Comments: 13 pages, 6 figures, 7 tables, accepted for publication by MNRAS

In this work, we test the hypothesis that narrow-line Seyfert 1 galaxies (NSL1s) are active galactic nuclei in their early phase and are therefore younger and more active than the more common broad-line Seyfert 1 galaxies (BLS1s). If that is true, then NLS1s should, on average, have lower black hole masses and higher accretion rates than BLS1s. To test this, we use a sample of 35 NLS1s and 54 BLS1s with similar X-ray luminosity distributions and good XMM-Newton observations. To determine the black hole mass, we apply an X-ray scaling method that is independent of any assumptions on the broad-line region dynamics and the inclination of the objects. We find that, on average, NLS1s have lower black hole masses, but the difference between the average black hole masses of NLS1s and BLS1s in our sample is only marginally significant (at the 2.6 sigma level). According to a Kolmogorov-Smirnov test, the distribution of black hole mass values of NLS1s is different from that of BLS1s at the 99% confidence level. Even stronger differences between NLS1s and BLS1s are inferred when the accretion rate distributions of NLS1s are compared to BLS1s, suggesting that the two populations are indeed distinct. Our study also indicates that the black hole mass values (both for NLS1s and BLS1s) determined with the X-ray scaling method are fully consistent with those obtained using reverberation mapping.

[292] arXiv:1807.05251v1 [pdf, vox]

Drifting Photons on Optical Paths: Mirrors, Sub-mm Resolution in 4 Dimensions, and Transverse/Longitudi​nal Phase Space: Exploiting Time Resolution

Henry J. Frisch
Submitted Friday 13 July 2018 @ 19:14:07 GMT
Invited Talk at the 5th International Conference on Micro-Pattern Gas Detectors (MPGD2017); Temple University, Philadelphia; May 2017

I discuss the status of MCP-based photo-detector amplification sections and Cherenkov light sources for precise timing measurements of charged particles and gamma rays. Sub-psec resolution is predicted for the large pulses such as those produced by a charged particle or electromagnetic shower traversing a photo-detector entrance window. Measuring events with sub-mm resolution in each of the 4 dimensions expands the optical phase space from 4 dimensions, allowing emittance transformations that can minimize expensive instrumented photo-sensitive area.

[293] arXiv:1807.05236v1 [pdf, vox]

Qualitative dynamics and inflationary attractors in loop cosmology

Bao-Fei Li, Parampreet Singh, Anzhong Wang
Submitted Friday 13 July 2018 @ 18:01:16 GMT
29 pages, 18 figures

Qualitative dynamics of three different loop quantizations of spatially flat isotropic and homogeneous models is studied using effective spacetime description of the underlying quantum geometry. These include the standard loop quantum cosmology (LQC), its recently revived modification (referred to as mLQC-I), and another related modification of LQC (mLQC-II) whose dynamics is studied in detail for the first time. Various features of LQC, including quantum bounce and pre-inflationary dynamics, are found to be shared with the mLQC-I and mLQC-II models. We study universal properties of dynamics for chaotic inflation, fractional monodromy inflation, Starobinsky potential, non-minimal Higgs inflation, and an exponential potential. We find various critical points and study their stability, which reveal various qualitative similarities in the post-bounce phase for all these models. The pre-bounce qualitative dynamics of LQC and mLQC-II turns out to be very similar, but is strikingly different from that of mLQC-I. In the dynamical analysis, some of the fixed points turn out to be degenerate for which center manifold theory is used. For all these potentials, non-perturbative quantum gravitational effects always result in a non-singular inflationary scenario with a phase of super-inflation succeeded by the conventional inflation. We show the existence of inflationary attractors, and obtain scaling solutions in the case of the exponential potential. Since all of the models agree with general relativity at late times, our results are also of use in classical theory where qualitative dynamics of some of the potentials has not been studied earlier.

[294] arXiv:1807.05233v1 [pdf, vox]

Counting of States in Higgs Theories

Mark P. Hertzberg, Mudit Jain
Submitted Friday 13 July 2018 @ 18:00:14 GMT
14 pages in double column format, 4 figures

We enumerate the micro-states in Higgs theories, addressing (i) the number of vacuum states and (ii) the appropriate measure in the quantum path integral. To address (i) we explicitly construct the set of ground state wave-functionals in the field basis focussing on scalar modes $\theta(x)$. Firstly, we show that in the limit in which the gauge coupling is zero, we obtain an infinite set of degenerate ground states at large volume distinguished by $\theta(x)\to\theta(​x)+\theta_0$, spontaneously breaking the global symmetry, as is well known. We then show that at finite gauge coupling there is a unique ground state at large volume since the wave-functional only depends on $\nabla\theta$ in the IR, and we explain this at the level of the Lagrangian. Since gauge fields fall off exponentially from sources there are no conserved charges or symmetries in the Higgs phase; so the Higgs mechanism is the removal of symmetry from the theory. We show how physical features of defects, such as cosmic strings in the abelian Higgs model, are best understood in this context. Since there is a unique ground state, we address (ii) whether the path integral is a volume measure for the radial Higgs field $\mathcal{D}\rho\,\r​ho^{N-1}$ from the $N$ components of the Higgs multiplet, or a line measure $\mathcal{D}\rho$ as the $N-1$ would-be Goldstones can be removed in unitary gauge. We prove that the need to avoid quartic divergences demands a tower of counter terms that resum to exactly give the volume measure. So the size of the Hilbert space in the zero gauge coupling case and finite gauge coupling case are in one-to-one correspondence, despite the degeneracy of the ground state being lifted in the latter. As a cosmological application, we point out that the volume measure can make it exponentially more unlikely in $N(=4)$ for the Standard Model Higgs to relax to the electroweak vacuum in the early universe.

[295] arXiv:1807.05230v1 [pdf, vox]

Studying the Milky Way Pulsar Population with Cosmic-Ray Leptons

Ilias Cholis, Tanvi Karwal, Marc Kamionkowski
Submitted Friday 13 July 2018 @ 18:00:01 GMT
14 pages, 7 figures and 4 tables

Recent measurements of cosmic-ray electron and positron spectra at energies from a GeV to 5 TeV, as well as radio, X-ray and a wide range of gamma-ray observations of pulsar-wind nebulae, indicate that pulsars are significant sources of high-energy cosmic-ray electrons and positrons. Here we calculate the local cosmic-ray $e^\pm$ energy spectra from pulsars taking into account models for (a) the distribution of the pulsars spin-down properties; (b) the cosmic-ray source spectra; and (c) the physics of cosmic-ray propagation. We then use the measured cosmic-ray fluxes from AMS-02, CALET and DAMPE to constrain the space of pulsar and cosmic-ray-propagati​on models and in particular, local cosmic-ray diffusion and energy losses, the pulsars' energy-loss time-dependence, and the injected $e^{\pm}$ spectra. We find that the lower estimates for the local $e^{\pm}$ energy losses are inconsistent with the data. We also find that pulsar braking indexes of 2.5 or less for sources with ages more than 10 kyr are strongly disfavored. Moreover, the cosmic-ray data are consistent with a wide range of assumptions on the $e^{\pm}$ injection spectral properties and on the distribution of initial spin-down powers. Above a TeV in energy, we find that pulsars can easily explain the observed change in the $e^{+} + e^{-}$ spectral slope. These conclusions are valid as long as pulsars contribute $\gtrsim10\%$ of the observed cosmic-ray $e^\pm$ at energies $\gtrsim100$ GeV.

[296] arXiv:1807.05231v1 [pdf, vox]

Carbon Chain Molecules Toward Embedded Low-Mass Protostars

Charles J. Law, Karin I. Oberg, Jennifer B. Bergner, Dawn Graninger
Submitted Friday 13 July 2018 @ 18:00:01 GMT
31 pages, 14 figures, accepted for publication in ApJ

Carbon chain molecules may be an important reservoir of reactive organics during star and planet formation. Carbon chains have been observed toward several low-mass young stellar objects (YSOs), but their typical abundances and chemical relationships in such sources are largely unconstrained. We present a carbon chain survey toward 16 deeply embedded (Class 0/I) low-mass protostars made with the IRAM 30 m telescope. Carbon chains are found to be common at this stage of protostellar evolution. We detect CCS, CCCS, HC$_3$N, HC$_5$N, l-C$_3$H, and C$_4$H toward 88%, 38%, 75%, 31%, 81%, and 88% of sources, respectively. Derived column densities for each molecule vary by one to two orders of magnitude across the sample. As derived from survival analysis, median column densities range between 1.2$\times 10^{11}$ cm$^{-2}$ (CCCS) and 1.5$\times 10^{13}$ cm$^{-2}$ (C$_4$H) and estimated fractional abundances with respect to hydrogen range between 2$\times 10^{-13}$ (CCCS) and 5$\times 10^{-11}$ (C$_4$H), which are low compared to cold cloud cores, warm carbon chain chemistry (WCCC) sources, and protostellar model predictions. We find significant correlations between molecules of the same carbon chain families, as well as between the cyanpolyynes (HC$_{\rm n}$N) and the pure hydrocarbon chains (C$_{\rm n}$H). This latter correlation is explained by a closely-related production chemistry of C$_{\rm{n}}$H and cyanpolyynes during low-mass star formation.

[297] arXiv:1807.05229v1 [pdf, vox]

A Robust Tip of the Red Giant Branch Distance to the Fireworks Galaxy (NGC 6946)

Gagandeep S. Anand, Luca Rizzi, R. Brent Tully
Submitted Friday 13 July 2018 @ 18:00:00 GMT
Accepted for publication in AJ, 11 pages, 8 figures

Archival HST data taken in F606W+F814W of two different fields in the outer regions of NGC 6946 is used to measure a tip of the red giant branch (TRGB) distance to the galaxy. We employ a Bayesian maximum-likelihood modeling method that incorporates the completeness of the photometry, and allows us to model the luminosity function of the RGB population. Our two fields provide us with distances of 7.74 $\pm$ 0.42 Mpc and 7.69 $\pm$ 0.50 Mpc, respectively. Our final distance of 7.72 $\pm$ 0.32 Mpc is higher than most values published previously in the literature. This has important implications for supernova measurements, as NGC 6946 is host to the most observed supernovae (10) of any galaxy to date. We find that the supernovae in NGC 6946 are on average $\sim$ 2.3 times more luminous than previous estimates. Our distance gives NGC 6946 a peculiar velocity of $v_{pec}$ = $-229$ $\pm$ $29$ km/s in the Local Sheet frame. This velocity is the projected component of a substantial negative SGZ motion, indicating a coherent motion along with the other members of the M101 wall toward the plane of the Local Sheet. The M101 wall, a spur off the Local Sheet into the Local Void, is experiencing the expansion of the Local Void.

[298] arXiv:1807.05210v1 [pdf, vox]

Active galactic nuclei with GeV activities and the PeV neutrino source candidate TXS 0506+056

Neng-Hui Liao, Yu-Liang Xin, Yun-Feng Liang, Xiao-Lei Guo, Shang Li, Hao-Ning He, Qiang Yuan, Yi-Zhong Fan
Submitted Friday 13 July 2018 @ 17:58:12 GMT
23 pages, 8 figures, 1 table

On 2017 September 22 the IceCube neutrino observatory detected a track-like, very-high-energy event (IceCube-170922A) that is spatially associated with TXS 0506+056, a quasar at a redshift of $z=0.3365$. This source is characterized by the increased acitivies in a very wide energy range (from radio to TeV) during these days. To investigate the possible connection of the PeV neutrino emission with the GeV activity of blazars, in this work we select 116 bright sources and analyze their lightcurves and spectra. We focus on the sources displaying GeV activities. Among these blazars, TXS 0506+056 seems to be typical in many aspects but is distinguished by the very strong GeV activties. We suggest to search for neutrino outburst in the historical data of IceCube, as recently done for TXS 0506+056, from the directions of these more energetic and harder blazars with strong GeV activities.

[299] arXiv:1807.05188v1 [pdf, vox]

Testing for directionality in the Planck polarization and lensing data

Majd Ghrear, Emory F. Bunn, Dagoberto Contreras, Douglas Scott
Submitted Friday 13 July 2018 @ 17:19:40 GMT
12 pages, 13 figures

In order to better analyse the polarization of the cosmic microwave background (CMB), which is dominated by emission from our Galaxy, we need tools that can detect residual foregrounds in cleaned CMB maps. Galactic foregrounds introduce statistical anisotropy and directionality to the polarization pseudo-vectors of the CMB, which can be investigated by using the D statistic of Bunn and Scott. This statistic is rapidly computable and capable of investigating a broad range of data products for directionality. We demonstrate the application of this statistic to detecting foregrounds in polarization maps by analysing the uncleaned Planck frequency maps. For the Planck CMB maps, we find no evidence for residual foreground contamination; however, we detect an excess directionality due to anisotropic noise, which can be dealt with through careful simulations. In order to examine the sensitivity of the D statistic, we add a varying fraction of the polarized thermal dust and synchrotron foreground maps to the CMB maps and show that roughly per-cent-level foreground contamination would be detected with 95 per cent confidence. We also demonstrate application of the D statistic to another data product by analysing the gradient of the minimum-variance CMB lensing potential map (i.e., the deflection angle) for directionality. We find no excess directionality in the lensing potential map when compared to the simulations provided by the Planck Collaboration.

[300] arXiv:1807.05180v1 [pdf, vox]

Predictably Missing Satellites: Subhalo Abundance in Milky Way-like Halos

Catherine E. Fielder, Yao-Yuan Mao, Jeffrey A. Newman, Andrew R. Zentner, Timothy C. Licquia
Submitted Friday 13 July 2018 @ 17:06:55 GMT
21 pages, 11 figures, submitted to Monthly Notices of the Royal Astronomical Society

On small scales there have been a number of claims of discrepancies between the standard Cold Dark Matter (CDM) model and observations. The 'missing satellites problem' infamously describes the overabundance of subhalos from CDM simulations compared to the number of satellites observed in the Milky Way. A variety of solutions to this discrepancy have been proposed; however, the impact of the specific properties of the Milky Way halo relative to the typical halo of its mass have yet to be explored. Motivated by recent studies that identified ways in which the Milky Way is atypical (e.g., Licquia et al. 2015), we investigate how the properties of dark matter halos with mass comparable to our Galaxy's --- including concentration, spin, shape, and scale factor of the last major merger --- correlate with the subhalo abundance. Using zoom-in simulations of Milky Way-like halos, we build two models of subhalo abundance as functions of host halo properties and conclude that the Milky Way should be expected to have 22%-44% fewer subhalos with low maximum rotation velocities ($V_{\rm max}^{\rm sat} \sim 10$kms$^{-1}$) at the 95% confidence level and up to 72% fewer than average subhalos with high rotation velocities ($V_{\rm max}^{\rm sat} \gtrsim 30$kms$^{-1}$, comparable to the Magellanic Clouds) than would be expected for a typical halo of the Milky Way's mass. Concentration is the most informative single parameter for predicting subhalo abundance. Our results imply that models tuned to explain the missing satellites problem assuming typical subhalo abundances for our Galaxy will be over-correcting.

[301] arXiv:1807.05179v1 [pdf, vox]

Kpc-scale radio-jets in narrow-line Seyfert 1 galaxies

Veeresh Singh, Hum Chand, C. H. Ishwara-Chandra, Preeti Kharb
Submitted Friday 13 July 2018 @ 17:00:33 GMT
6 pages, 4 figures, 1 table, accepted for publication in Proceedings of Science. Contributed article in the conference on "Revisiting narrow-line Seyfert 1 galaxies and their place in the Universe'' held in Padova university, Italy, 9-13 April 2018

Narrow-Line Seyfert 1 galaxies (NLS1s) are generally believed to be radio-quiet Active Galactic Nuclei (AGN) with relatively less-massive (10$^{5}$$-$10$^{8}$​~M$_{\odot}$) Super-Massive Black Holes (SMBH). Using the FIRST radio detections of hitherto the largest sample of 11101 optically-selected NLS1s we find a rather uncommon population of 55 NLS1s with Kiloparsec-Scale Radio structures (KSRs). We note that the number of NLS1s with KSRs found in our study is only a lower limit considering the effects of sensitivity, spatial resolution and projection, and hence, the number of NLS1s with KSRs may be more common than thought earlier. The NLS1s with KSRs are distributed across a wide range of redshifts, flux densities and luminosities. NLS1s with KSRs tend to exhibit steep radio spectra and are likely to be misaligned version of blazar-like NLS1s. The ratio of IR to radio flux density (q$_{\rm 22~{\mu}m}$ $=$ log[S$_{\rm 22~{\mu}m}$/S$_{\rm 1.4~GHz}$]) versus radio luminosity plot suggests that KSRs are mostly powered by AGN, while KSRs in NLS1s with low radio luminosity (L$_{\rm 1.4~GHz}$ $<$ 10$^{23.5}$ W~Hz$^{-1}$) may have a contribution from circumnuclear starburst. The trend shown by KSRs in radio luminosity versus radio-size plot indicates that the radio-jets resulting in KSRs are either in the early phase of their evolution or inefficient to grow beyond the host galaxy.

[302] arXiv:1807.05178v1 [pdf, vox]

Beaming electromagnetic (or heat-flux) instabilities from the interplay with the electron temperature anisotropies

S. M. Shaaban, M. Lazar, P. H. Yoon, S. Poedts
Submitted Friday 13 July 2018 @ 16:51:57 GMT
accepted for publication in Physics of Plasmas

In space plasmas kinetic instabilities are driven by the beaming (drifting) components and/or the temperature anisotropy of charged particles. The heat-flux instabilities are known in the literature as electromagnetic modes destabilized by the electron beams (or strahls) aligned to the interplanetary magnetic field. A new kinetic approach is proposed here in order to provide a realistic characterization of heat-flux instabilities under the influence of electrons with temperature anisotropy. Numerical analysis is based on the kinetic Vlasov-Maxwell theory for two electron counter-streaming (core and beam) populations with temperature anisotropies, and stationary, isotropic protons. The main properties of electromagnetic heat-flux instabilities are found to be markedly changed by the temperature anisotropy of electron beam $A_b = T_\perp / T_\parallel \ne 1$, leading to stimulation of either the whistler branch if $A_b > 1$, or the firehose branch for $A_b<1$. For a high temperature anisotropy whistlers switch from heat-flux to a standard regime, when their instability is inhibited by the beam.

[303] arXiv:1807.05170v1 [pdf, vox]

On Possibility of Determining Neutrino Mass Hierarchy by the Charged-Current and Neutral-Current Events of Supernova Neutrinos in Scintillation Detectors

Fei-Fan Lee, Feng-Shiuh Lee, Kwang-Chang Lai
Submitted Friday 13 July 2018 @ 16:42:00 GMT
one column, 16 pages, 2 figures

One of the unresolved mysteries in neutrino physics is the neutrino mass hierarchy. We present a new method to determine neutrino mass hierarchy by comparing the events of inverse beta decays (IBD), $\bar{\nu}_e + p\rightarrow n + e^+$, and neutral current (NC) interactions, $\nu(\overline{\nu}) + p\rightarrow\nu(\ove​rline{\nu}) + p$, of supernova neutrinos from accretion and cooling phases in scintillation detectors. Supernova neutrino flavor conversions depend on the neutrino mass hierarchy. On account of Mikheyev-Smirnov-Wol​fenstein effects, the full swapping of $\bar{\nu}_e$ flux with the $\bar{\nu}_x$ ($x=\mu,~\tau$) one occurs in the inverted hierarchy, while such a swapping does not occur in the normal hierarchy. In consequence, the ratio of high energy IBD events to NC events for the inverted hierarchy is higher than in the normal hierarchy. Since the luminosity of $\bar{\nu}_e$ is larger than that of $\nu_x$ in accretion phase while the luminosity of $\bar{\nu}_e$ becomes smaller than that of $\nu_x$ in cooling phase, we calculate this ratio for both accretion and cooling phases. By analyzing the change of this event ratio from accretion phase to cooling phase, one can determine the neutrino mass hierarchy.

[304] arXiv:1807.05226v1 [pdf, vox]

Measuring the viewing angle of binary neutron star mergers

Hsin-Yu Chen, Salvatore Vitale, Ramesh Narayan
Submitted Friday 13 July 2018 @ 16:08:30 GMT

The joint detection of GW170817 and its electromagnetic counterparts GRB170817A and kilonova AT 2017gfo has triggered extensive study of the electromagnetic emission of binary neutron star mergers. If a binary is viewed from different angles, the electromagnetic signatures can be distinct depending on the structure of the emission. Connecting electromagnetic observations to the inclination angle of the binary orbital plane is therefore crucial. We present a systematic study of how well ground-based gravitational-wave detectors can constrain the viewing angle of binary neutron star mergers. We find that, if the sky position and the redshift of the binary can be identified independently, e.g. via the electromagnetic counterpart and an associated host galaxy, for 50$\%$ of the systems the viewing angle can be constrained to $\leq 7^{\circ}$ uncertainty, independent of electromagnetic emission models. On the other hand, if no redshift measurement is available, the measurement of the viewing angle with gravitational-data alone is not informative, unless the true viewing angle is close to $90^{\circ}$. This holds true even if the sky position is measured independently.

[305] arXiv:1807.05155v1 [pdf, vox]

Limits on Neutrino Lorentz Violation from Multimessenger Observations of TXS 0506+056

John Ellis, Nikolaos E. Mavromatos, Alexander S. Sakharov, Edward K. Sarkisyan-Grinbaum
Submitted Friday 13 July 2018 @ 16:01:33 GMT
9 pages, no figures

The observation by the IceCube Collaboration of a high-energy ($E \gtrsim 200$ TeV) neutrino from the direction of the blazar TXS 0506+056 and the coincident observations of enhanced $\gamma$-ray emissions from the same object by MAGIC and other experiments can be used to set stringent constraints on Lorentz violation in the propagation of neutrinos that is linear in the neutrino energy: $\Delta v = - E/M_1$, where $\Delta v$ is the deviation from the velocity of light, and $M_1$ is an unknown high energy scale to be constrained by experiment. Allowing for a difference in neutrino and photon propagation times of $\sim 10$ days, we find that $M_1 \gtrsim 3 \times 10^{16}$ GeV. This improves on previous limits on linear Lorentz violation in neutrino propagation by many orders of magnitude, and the same is true for quadratic Lorentz violation.

[306] arXiv:1807.05144v1 [pdf, vox]

Sulphur-bearing molecules in AGB stars II: Abundances and distributions of CS and SiS

T. Danilovich, S. Ramstedt, D. Gobrecht, L. Decin, E. De Beck, H. Olofsson
Submitted Friday 13 July 2018 @ 15:41:14 GMT

We surveyed 20 AGB stars of different chemical types using the APEX telescope, and combined this with an IRAM 30 m and APEX survey of CS and SiS emission towards over 30 S-type stars. For those stars with detections, we performed radiative transfer modelling to determine abundances and abundance distributions. We detect CS towards all the surveyed carbon stars, some S-type stars, and the highest mass-loss rate oxygen-rich stars ($> 5\times 10^{-6}$ Msol yr$^{-1}$). SiS is detected towards the highest mass-loss rate sources of all chemical types ($> 8\times 10^{-7}$ Msol yr$^{-1}$). We find CS peak fractional abundances ranging from ~ $ 4\times 10^{-7}$ to ~ $2\times 10^{-5}$ for the carbon stars, from ~ $ 3\times 10^{-8}$ to ~ $1\times 10^{-7}$ for the oxygen-rich stars and from ~ $ 1\times 10^{-7}$ to ~ $8\times 10^{-6}$ for the S-type stars. We find SiS peak fractional abundances ranging from ~ $ 9\times 10^{-6}$ to ~ $ 2\times 10^{-5}$ for the carbon stars, from ~ $ 5\times 10^{-7}$ to ~ $ 2\times 10^{-6}$ for the oxygen-rich stars, and from ~ $ 2\times 10^{-7}$ to ~ $ 2\times 10^{-6}$ for the S-type stars. We derived Si$^{32}$S/Si$^{34}$​S = 11.4 for AI Vol, the only star for which we had a reliable isotopologue detection. Overall, we find that wind density plays an important role in determining the chemical composition of AGB CSEs. It is seen that for oxygen-rich AGB stars both CS and SiS are detected only in the highest density circumstellar envelopes and their abundances are generally lower than for carbon-rich AGB stars by around an order of magnitude. For carbon-rich and S-type stars SiS was also only detected in the highest density circumstellar envelopes, while CS was detected consistently in all surveyed carbon stars and sporadically among the S-type stars.

[307] arXiv:1807.05136v1 [pdf, vox]

Exoplanet Atmosphere Measurements from Direct Imaging

Beth A. Biller, Mickaël Bonnefoy
Submitted Friday 13 July 2018 @ 15:26:51 GMT
29 pages, 8 figures, authors' updated version of invited review chapter accepted for publication in the Handbook of Exoplanets

In the last decade, about a dozen giant exoplanets have been directly imaged in the IR as companions to young stars. With photometry and spectroscopy of these planets in hand from new extreme coronagraphic instruments such as SPHERE at VLT and GPI at Gemini, we are beginning to characterize and classify the atmospheres of these objects. Initially, it was assumed that young planets would be similar to field brown dwarfs, more massive objects that nonetheless share similar effective temperatures and compositions. Surprisingly, young planets appear considerably redder than field brown dwarfs, likely a result of their low surface gravities and indicating much different atmospheric structures. Preliminarily, young free-floating planets appear to be as or more variable than field brown dwarfs, due to rotational modulation of inhomogeneous surface features. Eventually, such inhomogeneity will allow the top of atmosphere structure of these objects to be mapped via Doppler imaging on extremely large telescopes. Direct imaging spectroscopy of giant exoplanets now is a prelude for the study of habitable zone planets. Eventual direct imaging spectroscopy of a large sample of habitable zone planets with future telescopes such as LUVOIR will be necessary to identify multiple biosignatures and establish habitability for Earth-mass exoplanets in the habitable zones of nearby stars.

[308] arXiv:1807.05120v1 [pdf, vox]

Thermal convection in rotating spherical shells: temperature-dependen​t internal heat generation using the example of triple-$α$ burning

F. Garcia, F. R. N Chambers, A. L. Watts
Submitted Friday 13 July 2018 @ 15:02:12 GMT
9 Figures, 6 Tables. Submitted to Physical Review Fluids

We present an exhaustive study of Boussinesq thermal convection including a temperature-dependen​t internal heating source, based on numerical three-dimensional simulations. The temperature dependence mimics triple alpha nuclear reactions and the fluid geometry is a rotating spherical shell. These are key ingredients for the study of convective accreting neutron star oceans. A new dimensionless parameter Ran , measuring the relevance of nuclear heating, is defined. We explore how flow characteristics change with increasing Ran and give an astrophysical motivation. The onset of convection is investigated with respect to the new parameter and periodic, quasiperiodic, chaotic flows with coherent structures, and fully turbulent flows are exhibited as Ran is varied. Several regime transitions are identified and compared with previous results on differentially heated convection. Finally, we explore (tentatively) the potential applicability of our results to the evolution of thermonuclear bursts in accreting neutron star oceans.

[309] arXiv:1807.05113v1 [pdf, vox]

A hadronuclear interpretation of a high-energy neutrino event coincident with a blazar flare

Ruo-Yu Liu, Kai Wang, Rui Xue, Andrew M. Taylor, Xiang-Yu Wang, Zhuo Li, Huirong Yan
Submitted Friday 13 July 2018 @ 14:52:44 GMT
13 pages, 7 figures, 1 table

Although many high-energy neutrinos detected by the IceCube telescope are believed to have an extraterrestrial origin, their astrophysical sources remain a mystery. Recently, an unprecedented discovery of a high-energy muon neutrino event coincident with a multiwavelength flare from a blazar, TXS~0506+056, shed some light on the origin of the neutrinos. It is usually believed that a blazar is produced by a relativistic jet launched from an accreting supermassive black hole (SMBH). Here we show that the high-energy neutrino event can be interpreted by the inelastic hadronuclear interactions between the accelerated cosmic-ray protons in the relativistic jet and the dense gas clouds in the vicinity of the SMBH. Such a scenario only requires a moderate proton power in the jet, which could be much smaller than that required in the conventional hadronic model which instead calls upon the photomeson process. Meanwhile, the flux of the multiwavelength flare from the optical to gamma-ray band can be well explained by invoking a second radiation zone in the jet at a larger distance to the SMBH.

[310] arXiv:1807.05095v1 [pdf, vox]

Do the Pulsation Properties of Red Giants Vary around their Long Secondary Period Cycle?

John Percy, Kunming Di
Submitted Friday 13 July 2018 @ 14:10:36 GMT
To be submitted to JAAVSO

We have used visual and Johnson V observations from the American Association of Variable Star Observers (AAVSO) International Database, and the AAVSO VSTAR time-series package, and (O-C) analysis to investigate possible changes in the pulsation period and amplitude of the pulsating red giants U Del, EU Del, X Her, and Y Lyn around the cycle of their long secondary periods (LSPs). We find no such changes in period or amplitude. This suggests (weakly) that the process -- whatever it is -- that causes the LSPs does not significantly change the physical properties of the visible hemisphere of the stars as the LSP cycle proceeds.

[311] arXiv:1807.05089v1 [pdf, vox]

ERIS: revitalising an adaptive optics instrument for the VLT

Richard Davies, Simone Esposito, Hans Martin Schmid, William Taylor, Guido Agapito, Alexander Agudo Berbel, Andrea Baruffolo, Valdemaro Biliotti, Beth Biller, Martin Black, Anna Boehle, Runa Briguglio, Alexander Buron, Luca Carbonaro, Angela Cortes, Giovanni Cresci, Matthias Deysenroth, Amico Di Cianno, Gianluca Di Rico, David Doelman, Mauro Dolci, Reinhold Dorn, Frank Eisenhauer, Daniela Fantinel, Debora Ferruzzi, Helmut Feuchtgruber, Natascha Förster Schreiber, Xiaofeng Gao, Hans Gemperlein, Reinhard Genzel,