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Astrophysics

Thu, 14 Dec 2017

Showing 100 entries from Tue, 12 Dec 2017 to Wed, 13 Dec 2017

Submitted Wed, 13 Dec 2017

[1] arXiv:1712.04932v1 [pdf, vox]

Index catalogue for the "Izvestiya Krymskoj Astrofizicheskoj Observatorii" publications

K. V. Logachev, A. A. Shlyapnikov
Submitted Wednesday 13 December 2017 @ 18:58:12 GMT
4 pages, in Russian, 2 figures, 4 references

Information on the creation of the index-catalogue for articles published in the journal "Izvestia of the Crimean Astrophysical Observatory" ("Izvestiya Krymskoj Astrofizicheskoj Observatorii" from ADS Bibliographic Codes: Journal Abbreviation - IzKry) is presented. A brief history of the accumulation of references for the catalog, its structure and the scheme of interaction with the basic world astronomical databases are described.

[2] arXiv:1712.04928v1 [pdf, vox]

Fundamental Physics with the Hubble Space Telescope

Neal Dalal, Cora Dvorkin, Jeremy Heyl, Bhuvnesh Jain, Marc Kamionkowski, Phil Marshall, David Weinberg
Submitted Wednesday 13 December 2017 @ 18:55:21 GMT
Report of the HST and Fundamental Physics Working Group, constituted by STScI Director Ken Sembach to identify ways that HST could enable advances in fundamental physics

Cosmology is intrinsically intertwined with questions in fundamental physics. The existence of non-baryonic dark matter requires new physics beyond the Standard Model of elemenatary-particle interactions and Einstein's general relativity, as does the accelerating expansion of the universe. Current tensions between various cosmological measurements may be harbingers of yet more new physics. Progress on understanding dark matter and cosmic acceleration requires long term, high-precision measurements and excellent control of systematics, demanding observational programs that are often outside the discovery/characteri​zation mode that drives many areas of astronomy. We outline potential programs through which the Hubble Space Telescope (HST) could have a major impact on issues in fundamental physics in the coming years. To realize this impact, we suggest the introduction of a "HST Fundamental Physics" observational program that would be subject to a modified proposal and review process.

[3] arXiv:1712.04923v1 [pdf, vox]

The skewed weak lensing likelihood: why biases arise, despite data and theory being sound

Elena Sellentin, Catherine Heymans, Joachim Harnois-Déraps
Submitted Wednesday 13 December 2017 @ 18:52:01 GMT
Submitted to MNRAS

We derive the essentials of the skewed weak lensing likelihood via a simple Hierarchical Model. Our likelihood passes four objective and cosmology-independen​t tests which a standard Gaussian likelihood fails. We demonstrate that sound weak lensing analyses are naturally biased low, and this does not indicate any new physics such as deviations from $\Lambda$CDM. Mathematically, the biases arise because noisy two-point functions follow skewed distributions. This form of bias is already known from CMB analyses, where the low multipoles have asymmetric error bars. Weak lensing is more strongly affected by this asymmetry as galaxies form a discrete set of shear tracer particles, in contrast to a smooth shear field. We demonstrate that the biases can be up to 30 percent of the standard deviation per data point, dependent on the properties of the weak lensing survey. Our likelihood provides a versatile framework with which to address this bias in future weak lensing analyses.

[4] arXiv:1712.04913v1 [pdf, vox]

Arp 202: a TDG formed in a parent's extended dark matter halo?

T. C. Scott, P. Lagos, S. Ramya, C. Sengupta, S. Paudel, D. K. Sahu, K. Misra, J. -H. Woo, B. W. Soh
Submitted Wednesday 13 December 2017 @ 18:32:46 GMT
13 pages, 6 figures

We report on H${\alpha}$ + [NII] imaging of the Arp 202 interacting pair and its tidal dwarf galaxy (TDG) candidate as well as a GMOS long slit spectrum from the TDG candidate, observed with the Gemini North telescope. Our H${\alpha}$ + [NII] imaging reveals the TDG to have an elongated structure, $\sim$ 1.9 kpc in length with the two principal star forming knots at either end. Our observations also show the TDG candidate has a recessional V$_{H\alpha}$ $\sim$ 3032 km s$^{-1}$, within 100 km s$^{-1}$ of the parent pair's mean velocity and an oxygen abundance of 12+log(O/H) = 8.10$\pm$0.41. The TDG's oxygen abundance is in good agreement with that of a star forming region in NGC 2719A, one of the parent galaxies, which has an estimated oxygen abundance of 12+log(O/H) = 8.05$\pm$0.41. The TDG's V$_{H\alpha}$ and oxygen abundance confirm previous results validating the candidate as a TDG. The absence of detectable emission from the TDG in $\textit{Spitzer}$ 3.6 $\mu$m and 4.5 $\mu$m images together with the lack of absorption lines and weak continuum in the spectrum is consistent with absence of an old population ($\gtrsim$ 0.5 Gyr). The location of the TDG within the interaction debris and the absence of indicators of an old stellar population in the TDG are consistent with a scenario in which the TDG is formed from HI stripped from the parent galaxies and within the extended dark matter halo of one of the parents as proposed by (Bournaud et al. 2003; Duc et al. 2004).

[5] arXiv:1712.04901v1 [pdf, vox]

Earth-Scattering of super-heavy Dark Matter: updated constraints from detectors old and new

Bradley J. Kavanagh
Submitted Wednesday 13 December 2017 @ 18:14:00 GMT
10 pages, 6 figures. Code available at https://github.com/b​radkav/verne. Comments welcome

Direct searches for Dark Matter (DM) are continuously improving, probing down to lower and lower DM-nucleon interaction cross sections. For strongly-interacting massive particle (SIMP) Dark Matter, however, the accessible cross section is bounded from above due to the stopping effect of the atmosphere, Earth and detector shielding. We present a careful calculation of the SIMP signal rate, focusing on super-heavy DM ($m_\chi \gtrsim 10^5 \,\,\mathrm{GeV}$), where the standard nuclear-stopping formalism is applicable. With recent results from the low-threshold, surface-operated $\nu$-cleus experiment, we improve the maximum cross section reach of direct detection searches by a factor of around 5000, for DM masses up to $10^8 \,\,\mathrm{GeV}$. A reanalysis of the longer-exposure, sub-surface CDMS-I results (published in 2002) improves the previous cross section reach by two orders of magnitude, for masses up to $10^{15} \,\,\mathrm{GeV}$. Along with complementary constraints from SIMP capture and annihilation in the Earth and Sun, these improved limits from direct nuclear scattering searches close a number of windows in the SIMP parameter space in the mass range $10^6$ GeV to $10^{13}$ GeV, of particular interest for heavy DM produced gravitationally at the end of inflation.

[6] arXiv:1712.04874v1 [pdf, vox]

Quantum corrections to quartic inflation with a non-minimal coupling: metric vs. Palatini

Tommi Markkanen, Tommi Tenkanen, Ville Vaskonen, Hardi Veermäe
Submitted Wednesday 13 December 2017 @ 17:31:52 GMT
16 pages

We study models of quartic inflation where the inflaton field $\phi$ is coupled non-minimally to gravity, $\xi \phi^2 R$, and perform a study of quantum corrections in curved space-time at one-loop level. We specifically focus on comparing results between the metric and Palatini theories of gravity. Transformation from the Jordan to the Einstein frame gives different results for the two formulations. By using an effective field theory expansion we derive the appropriate $\beta$-functions and the renormalisation group improved effective potentials in curved space for both cases in the Einstein frame. In particular, we show that in both formalisms the Einstein frame depends on the order of perturbation theory but that the flatness of the potential is unaltered by quantum corrections.

[7] arXiv:1712.04872v1 [pdf, vox]

A Recurrent Nova Super-Remnant in the Andromeda Galaxy

M. J. Darnley, R. Hounsell, T. J. O'Brien, P. Rodríguez-Gil, A. W. Shafter, M. M. Shara, M. Henze, M. F. Bode, R. Galera-Rosillo, D. J. Harman, J. -U. Ness, V. A. R. M. Ribeiro, N. M. H. Vaytet, S. C. Williams
Submitted Wednesday 13 December 2017 @ 17:27:33 GMT
30 pages, 8 figures

Here we report that the most rapidly recurring nova, M31N 2008-12a, which erupts annually, is surrounded by a "nova super-remnant" which demonstrates that M31N 2008-12a has erupted with high frequency for millions of years.

[8] arXiv:1712.04865v1 [pdf, vox]

Model-independent cosmological constraints from growth and expansion

Benjamin L'Huillier, Arman Shafieloo, Hyungjin Kim
Submitted Wednesday 13 December 2017 @ 17:10:48 GMT
7pages, 8 figures

Reconstructing the expansion history of the Universe from type Ia supernovae data, we fit the growth rate measurements and put model-independent constraints on some key cosmological parameters, namely, $\Omega_\mathrm{m},\​gamma$, and $\sigma_8$. The constraints are consistent with those from the concordance model within the framework of general relativity, but the current quality of the data is not sufficient to rule out modified gravity models. Adding the condition that dark energy density should be positive at all redshifts, independently of its equation of state, further constrains the parameters and interestingly supports the concordance model.

[9] arXiv:1712.04855v1 [pdf, vox]

The Trojan Color Conundrum

David Jewitt
Submitted Wednesday 13 December 2017 @ 16:41:43 GMT
The Astronomical Journal, in press; 3 figures, 4 tables

The Trojan asteroids of Jupiter and Neptune are likely to have been captured from original heliocentric orbits in the dynamically excited ("hot") population of the Kuiper belt. However, it has long been known that the optical color distributions of the Jovian Trojans and the hot population are not alike. This difference has been reconciled with the capture hypothesis by assuming that the Trojans were resurfaced (for example, by sublimation of near-surface volatiles) upon inward migration from the Kuiper belt (where blackbody temperatures are $\sim$40 K) to Jupiter's orbit ($\sim$125 K). Here, we examine the optical color distribution of the \textit{Neptunian} Trojans using a combination of new optical photometry and published data. We find a color distribution that is statistically indistinguishable from that of the Jovian Trojans but unlike any sub-population in the Kuiper belt. This result is puzzling, because the Neptunian Trojans are very cold (blackbody temperature $\sim$50 K) and a thermal process acting to modify the surface colors at Neptune's distance would also affect the Kuiper belt objects beyond, where the temperatures are nearly identical. The distinctive color distributions of the Jovian and Neptunian Trojans thus present us with a conundrum: they are very similar to each other, suggesting either capture from a common source or surface modification by a common process. However, the color distributions differ from any plausible common source population, and there is no known modifying process that could operate equally at both Jupiter and Neptune.

[10] arXiv:1712.04852v1 [pdf, vox]

X-ray/UV/optical variability of NGC 4593 with Swift: Reprocessing of X-rays by an extended reprocessor

I M McHardy, S D Connolly, K Horne E M Cackett, J Gelbord, B M Peterson, M Pahari, N Gehrels, R Edelson, M Goad, P Lira, P Arevalo, R D Baldi, N Brandt, E Breedt, H Chand, G Dewangan, C Done, M Elvis, D Emmanoulopoulos, M M Fausnaugh, S Kaspi, C S Kochanek, K Korista, I E Papadakis, A R Rao, P Uttley, M Vestergaard, M J Ward
Submitted Wednesday 13 December 2017 @ 16:40:57 GMT
18 pages, 17 figures. Submitted to Monthly Notices of the Royal Astronomical Society

We report the results of intensive X-ray, UV and optical monitoring of the Seyfert 1 galaxy NGC 4593 with Swift. There is no intrinsic flux-related spectral change in the the variable components in any band with small apparent variations due only to contamination by a second constant component, possibly a (hard) reflection component in the X-rays and the (red) host galaxy in the UV/optical bands. Relative to the shortest wavelength band, UVW2, the lags of the other UV and optical bands are mostly in agreement with the predictions of reprocessing of high energy emission from an accretion disc. The U-band lag is, however, far larger than expected, almost certainly because of reprocessed Balmer continuum emission from the more distant broad line region gas. The UVW2 band is well correlated with the X-rays but lags by ~6x more than expected if the UVW2 results from reprocessing of X-rays on the accretion disc. However, if the lightcurves are filtered to remove variations on timescales >5d, the lag approaches the expectation from disc reprocessing. MEMEcho analysis shows that direct X-rays can be the driver of most of the variations in the UV/optical bands as long as the response functions for those bands all have long tails (up to 10d) in addition to a strong peak (from disc reprocessing) at short lag (<1d). We interpret the tails as due to reprocessing from the surrounding gas. Comparison of X-ray to UVW2 and UVW2 to V-band lags for 4 AGN, including NGC 4593, shows that all have UVW2 to V-band lags which exceed the expectations from disc resprocessing by factor < 2. However the X-ray to UVW2 lags are, mostly, in greater excess from the expectations from disc reprocessing and differ between AGN. The largest excess is in NGC 4151. Absorption and scattering may be affecting X-ray to UV lags.

[11] arXiv:1712.04843v1 [pdf, vox]

HERUS: The Far-IR/Submm Spectral Energy Distributions of Local ULIRGs & Photometric Atlas

D. L. Clements, C. Pearson, D. Farrah, J. Greenslade, Jeronimo Bernard-Salas, E. Gonzalez-Alfonso, J. Afonso, A. Efstathiou, D. Rigopoulou, V. Lebouteiller, P. D. Hurley, H. Spoon
Submitted Wednesday 13 December 2017 @ 16:21:49 GMT
Accepted for publication in MNRAS

We present the Herschel-SPIRE photometric atlas for a complete flux limited sample of 43 local Ultraluminous Infrared Galaxies (ULIRGs), selected at 60${\mu}$m by IRAS, as part of the HERschel ULIRG Survey (HERUS). Photometry observations were obtained using the SPIRE instrument at 250, 350 and 500${\mu}$m. We describe these observations, present the results, and combine the new observations with data from IRAS to examine the far-IR spectral energy distributions (SEDs) of these sources. We fit the observed SEDs of HERUS objects with a simple parameterised modified black body model where temperature and emissivity $\beta$ are free parameters. We compare the fitted values to those of non-ULIRG local galaxies, and find, in agreement with earlier results, that HERUS ULIRGs have warmer dust (median temperature T = 37.9+/-4.7 K compared to 21.3+/-3.4 K) but a similar $\beta$ distribution (median $\beta$ = 1.7 compared to 1.8) to the Herschel reference sample (HRS, Cortese et al., 2014) galaxies. Dust masses are found to be in the range of 10^7.5 to 10^9 Msun significantly higher than that of Herschel Reference Sample (HRS) sources. We compare our results for local ULIRGs with higher redshift samples selected at 250 and 850${\mu}$m. These latter sources generally have cooler dust and/or redder 100-to-250 ${\mu}$m colours than our 60${\mu}$m-selected ULIRGs. We show that this difference may in part be the result of the sources being selected at different wavelengths rather than being a simple indication of rapid evolution in the properties of the population.

[12] arXiv:1712.04841v1 [pdf, vox]

The Morphology of Disk Galaxies in Galaxy Clusters with Dark Matter Self-Interactions

Lucas F. Secco, Amanda Farah, Bhuvnesh Jain, Susmita Adhikari, Arka Banerjee, Neal Dalal
Submitted Wednesday 13 December 2017 @ 16:17:44 GMT
14 pages, 9 figures, 1 table

Self-Interacting Dark Matter (SIDM) has long been proposed as a solution to small scale problems posed by standard Cold Dark Matter (CDM). We use numerical simulations to study the effect of dark matter interactions on the morphology of disk galaxies falling into galaxy clusters. The effective drag force on dark matter leads to offsets of the stellar disk with respect to the surrounding halo, causing distortions in the disk. For anisotropic scattering cross-sections of 0.5 and 1.0$\,\textrm{cm}^{2​}\textrm{g}^{-1}$, we show that potentially observable warps, asymmetries, and thickening of the disk occur in simulations. We discuss the connection between these observational tests of SIDM and the follow up work needed with simulations in order to obtain detailed predictions.

[13] arXiv:1712.04831v1 [pdf, vox]

Impact of ultraluminous X-ray sources on photoabsorption in the first galaxies

Sergey Sazonov, Ildar Khabibullin
Submitted Wednesday 13 December 2017 @ 16:01:28 GMT
12 pages, 11 figures, submitted to MNRAS

In the local Universe, integrated X-ray emission from high-mass X-ray binaries (HMXBs) is dominated by the brightest ultraluminous X-ray sources (ULXs) with luminosity >~10^40 erg/s. Such rare objects probably also dominated the production of X-rays in the early Universe. We demonstrate that a ULX with Lx~10^40-10^41 erg/s (isotropic-equivalen​t luminosity in the 0.1-10 keV energy band) shining for ~10^5 years (the expected duration of a supercritically accreting phase in HMXBs) can significantly ionise the ISM in its host dwarf galaxy of mass M~10^7-10^8 Msun and thereby reduce its opacity to soft X-rays. As a result, the fraction of the soft X-ray (below 1 keV) radiation from the ULX escaping into the intergalactic medium (IGM) can increase from ~20-50% to ~30-80% over its lifetime. This implies that HMXBs can induce a stronger heating of the IGM at z>~10 compared to estimates neglecting the ULX feedback on the ISM. However, larger galaxies with M>~3x10^8 Msun could not be significantly ionised even by the brightest ULXs in the early Universe. Since such galaxies probably started to dominate the global star-formation rate at z<~10, the overall escape fraction of soft X-rays from the HMXB population probably remained low, <~30%, at these epochs.

[14] arXiv:1712.04827v1 [pdf, vox]

Self-gravitating $Λ$-media

Marco Celoria, Denis Comelli, Luigi Pilo
Submitted Wednesday 13 December 2017 @ 15:55:03 GMT
5 pages

We address the question whether a medium featuring $p+\rho =0$, dubbed $\Lambda$-medium, has to be necessarily a cosmological constant. By using effective field theory, we show that this is not the case for a class of media comprising perfect fluids, solids and special super solids, providing an explicit construction. The low energy excitations are non trivial and lensing and the growth of large scale structures can be used to clearly distinguish $\Lambda$-media from a cosmological constant.

[15] arXiv:1712.04810v1 [pdf, vox]

A general approach for testing non-cold dark matter at small cosmological scales

Riccardo Murgia
Submitted Wednesday 13 December 2017 @ 15:12:27 GMT
6 pages, 2 figures; to appear in the Proceedings of the 8th Young Researcher Meeting 2017

We present a general approach for modelling the small-scale suppression in the linear matter power spectrum induced by the presence of non-cold dark matter. We show that the new parametrisation accurately describes a large variety of non-thermal scenarios, removing the need to individually test each of them. We discuss the first astrophysical constraints on its free parameters and we outline the next steps for pursuing a full statistical data analysis.

[16] arXiv:1712.04806v1 [pdf, vox]

On the nature of fast radio bursts

Istomin Ya. N
Submitted Wednesday 13 December 2017 @ 14:58:14 GMT
8 pages, 4 figures

Scenario of formation of fast radio bursts (FRBs) is proposed. Just like radio pulsars, sources of FRBs are magnetized neutron stars. Appearance of strong electric field in a magnetosphere of a neutron star is associated with close passage of a dense body near hot neutron star. For the repeating source FRB 121102, which has been observed in four series of bursts, the period of orbiting of the body is about 200 days. Thermal radiation from the surface of the star (temperature is of the order of $ 10^8 \, K $) causes evaporation and ionization of the matter of the dense body. Ionized gas (plasma) flows around the magnetosphere of the neutron star with the velocity $ u \simeq 10^7 \, cm / s $, and creates electric potential $ \psi_0 \simeq 10^{11} \, V $ in the polar region of the magnetosphere. Electrons from the plasma flow are accelerated toward the star, and gain Lorentz factor of $ \simeq 10 ^ 5 $. Thermal photons moving toward precipitating electrons are scattered by them, and produce gamma photons with energies of $ \simeq 10^5 \, m_e c^2 $. These gamma quanta produce electron-positron pairs in collisions with thermal photons. The multiplicity, the number of born pairs per one primary electron, is about $ 10^5 $. The electron-positron plasma, produced in the polar region of magnetosphere, accumulates in a narrow layer at a bottom of a potential well formed on one side by a blocking potential $ \psi_0 $, and on the other side by pressure of thermal radiation. The density of electron-positron plasma in the layer increases with time, and after short time the layer becomes a mirror for thermal radiation of the star. The thermal radiation in the polar region under the layer is accumulated during time $ \simeq 500 \, s $, then the plasma layer is ejected outside. The ejection is observed as burst of radio emission formed by the flow of relativistic electron-positron plasma.

[17] arXiv:1712.04796v1 [pdf, vox]

Infrared spectra of complex organic molecules in astronomically relevant ice matrices. I. Acetaldehyde, ethanol, and dimethyl ether

J. Terwisscha van Scheltinga, N. F. W. Ligterink, A. C. A. Boogert, E. F. van Dishoeck, H. Linnartz
Submitted Wednesday 13 December 2017 @ 14:44:29 GMT
forthcoming paper in Astronomy & Astrophysics

Context. The number of identified complex organic molecules (COMs) in inter- and circumstellar gas-phase environments is steadily increasing. Recent laboratory studies show that many such species form on icy dust grains. At present only smaller molecular species have been directly identified in space in the solid state. Accurate spectroscopic laboratory data of frozen COMs, embedded in ice matrices containing ingredients related to their formation scheme, are still largely lacking. Aims. This work provides infrared reference spectra of acetaldehyde (CH$_3$CHO), ethanol (CH$_3$CH$_2$OH), and dimethyl ether (CH$_3$OCH$_3$) recorded in a variety of ice environments and for astronomically relevant temperatures, as needed to guide or interpret astronomical observations, specifically for upcoming James Webb Space Telescope observations. Methods. Fourier transform transmission spectroscopy (500-4000 cm$^{-1}$ / 20-2.5 $\mu$m, 1.0 cm$^{-1}$ resolution) was used to investigate solid acetaldehyde, ethanol and dimethyl ether, pure or mixed with water, CO, methanol, or CO:methanol. These species were deposited on a cryogenically cooled infrared transmissive window at 15~K. A heating ramp was applied, during which IR spectra were recorded until all ice constituents were thermally desorbed. Results. We present a large number of reference spectra that can be compared with astronomical data. Accurate band positions and band widths are provided for the studied ice mixtures and temperatures. Special efforts have been put into those bands of each molecule that are best suited for identification. For acetaldehyde the 7.427 and 5.803 $\mu$m bands are recommended, for ethanol the 11.36 and 7.240 $\mu$m bands are good candidates, and for dimethyl ether bands at 9.141 and 8.011 $\mu$m can be used. All spectra are publicly available in the Leiden Database for Ice.

[18] arXiv:1712.04793v1 [pdf, vox]

Identifying WIMP dark matter from particle and astroparticle data

Gianfranco Bertone, Nassim Bozorgnia, Jong Soo Kim, Sebastian Liem, Christopher McCabe, Sydney Otten, Roberto Ruiz de Austri
Submitted Wednesday 13 December 2017 @ 14:41:50 GMT
43 pages, 14 figures

One of the most promising strategies to identify the nature of dark matter consists in the search for new particles at accelerators and with so-called direct detection experiments. Working within the framework of simplified models, and making use of machine learning tools to speed up statistical inference, we address the question of what we can learn about dark matter from a detection at the LHC and a forthcoming direct detection experiment. We show that with a combination of accelerator and direct detection data, it is possible to identify newly discovered particles as dark matter, by reconstructing their relic density assuming they are weakly interacting massive particles (WIMPs) thermally produced in the early Universe, and demonstrating that it is consistent with the measured dark matter abundance. An inconsistency between these two quantities would instead point either towards additional physics in the dark sector, or towards a non-standard cosmology, with a thermal history substantially different from that of the standard cosmological model.

[19] arXiv:1712.04792v1 [pdf, vox]

Observational Constraints on Secret Neutrino Interactions from Big Bang Nucleosynthesis

Guo-yuan Huang, Tommy Ohlsson, Shun Zhou
Submitted Wednesday 13 December 2017 @ 14:41:10 GMT
18 pages, 5 figures

We investigate possible interactions between neutrinos and massive scalar bosons via $g^{}_{\phi} \overline{\nu} \nu \phi$ (or massive vector bosons via $g^{}_V \overline{\nu} \gamma^\mu \nu V^{}_\mu$) and explore the allowed parameter space of the coupling constant $g^{}_{\phi}$ (or $g^{}_V$) and the scalar (or vector) boson mass $m^{}_\phi$ (or $m^{}_V$) by requiring that these secret neutrino interactions (SNIs) should not spoil the success of Big Bang nucleosynthesis (BBN). Incorporating the SNIs into the evolution of the early Universe in the BBN era, we numercially solve the Boltzmann equations and compare the predictions for the abundances of light elements with observations. It turns out that the constraint on $g^{}_{\phi}$ and $m^{}_\phi$ in the scalar-boson case is rather weak, due to a small number of degrees of freedom. However, in the vector-boson case, the most stringent bound on the coupling $g^{}_V \lesssim 6\times 10^{-10}$ at $95~\%$ confidence level is obtained for $m^{}_V \simeq 1~{\rm MeV}$, while the bound becomes much weaker $g^{}_V \lesssim 8\times 10^{-6}$ for smaller masses $m^{}_V \lesssim 10^{-4}~{\rm MeV}$. Moreover, we discuss in some detail how the SNIs affect the cosmological evolution and the abundances of the lightest elements.

[20] arXiv:1712.04788v1 [pdf, vox]

Identification of SIPS~J2045$-$6332 as a partially resolved binary

Niall R Deacon, Kyle L Sobanja, Leigh C Smith
Submitted Wednesday 13 December 2017 @ 14:34:13 GMT
2 pages, 1 table, accepted for publication in RNAAS, abstract not included in research note

We show that SIPS J2045-6332, a late M/early L object previously identified as a candidate spectral mix binary, shows an elongated image shape. Using shape measurement techniques originally developed for cosmological weak lensing surveys on VISTA VHS images we show that this likely blended binary has an implied position angle of ~290 degrees East of North with a secondary companion that is likely to be a late L dwarf. This object would be a good follow-up target for high resolution imaging studies

[21] arXiv:1712.04785v1 [pdf, vox]

Characterizing TW Hydra

Kimberly R. Sokal, Casey P. Deen, Gregory N. Mace, Jae-Joon Lee, Heeyoung Oh, Hwihyun Kim, Benjamin T. Kidder, Daniel T. Jaffe
Submitted Wednesday 13 December 2017 @ 14:27:13 GMT
17 pages, 9 figures (one is a figure set that will be available in the online journal). Accepted by ApJ

At 60 pc, TW Hydra (TW Hya) is the closest example of a star with a gas-rich protoplanetary disk, though TW Hya may be relatively old (3-15 Myr). As such, TW Hya is especially appealing to test our understanding of the interplay between stellar and disk evolution. We present a high-resolution near-infrared spectrum of TW Hya obtained with the Immersion GRating INfrared Spectrometer (IGRINS) to re-evaluate the stellar parameters of TW Hya. We compare these data to synthetic spectra of magnetic stars produced by MoogStokes, and use sensitive spectral line profiles to probe the effective temperature, surface gravity, and magnetic field. A model with T_eff= 3800 K, log g=4.2, and B=3.0 kG best fits the near-infrared spectrum of TW Hya. These results correspond to a spectral type of M0.5 and an age of 8 Myr, which is well past the median life of gaseous disks.

[22] arXiv:1712.04779v1 [pdf, vox]

Exploring the astrophysics of dark atoms

Akshay Ghalsasi, Matthew McQuinn
Submitted Wednesday 13 December 2017 @ 14:13:30 GMT
20 pages and 7 figures

A component of the dark matter could consist of two darkly charged particles with a large mass ratio and a massless force carrier. This `atomic' dark sector could behave much like the baryonic sector, cooling and fragmenting down to stellar-mass or smaller scales. Past studies have shown that cosmic microwave background and large-scale structure constraints rule out $\gtrsim 5\%$ of the dark matter to behave in this manner. However, we show that, even with percent level mass fractions, a dark atomic sector could affect some extragalactic and galactic observables. We track the cooling and merger history of an atomic dark component for much of the interesting parameter space. Unlike the baryons, where stellar feedback (driven by nuclear physics) delays the formation and growth of galaxies, cooling dark atomic gas typically results in disks forming earlier, leaving more time for their destruction via mergers. Rather than disks in Milky Way sized halos, we find the end product is typically spheroidal structures on galactic scales or dark atom fragments distributed on halo scales. This result contrasts with previous studies, which had assumed that the dark atoms would result in dark disks. Furthermore the dark atoms condense into dense clumps, analogous to how the baryons fragment on solar-mass scales. We estimate the size of these dark clumps, and use these estimates to show that viable atomic dark matter parameter space is ruled out by stellar microlensing, by the half-light radii of ultra-faint dwarf galaxies, and by Milky Way mass-to-light inferences.

[23] arXiv:1712.04773v1 [pdf, vox]

Lepton-rich cold QCD matter in protoneutron stars

J. C. Jiménez, E. S. Fraga
Submitted Wednesday 13 December 2017 @ 14:06:03 GMT
9 pages, 8 figures

We investigate protoneutron star matter using the state-of-the-art perturbative equation of state for cold and dense QCD in the presence of a fixed lepton fraction in which both electrons and neutrinos are included. Besides computing the modifications in the equation of state due to the presence of trapped neutrinos, we show that stable strange quark matter has a more restricted parameter space. We also study the possibility of nucleation of unpaired quark matter in the core of protoneutron stars by matching the lepton-rich QCD pressure onto a hadronic equation of state, namely TM1 with trapped neutrinos. Using the inherent dependence of perturbative QCD on the renormalization scale parameter, we provide a measure of the uncertainty in the observables we compute.

[24] arXiv:1712.04766v1 [pdf, vox]

CMB from EFT

Sayantan Choudhury
Submitted Wednesday 13 December 2017 @ 13:53:28 GMT
77 pages

In this work, we study the key role of generic Effective Field Theory (EFT) framework to quantify the correlation functions in a quasi de Sitter background for an arbitrary initial choice of the quantum vacuum state. We perform the computation in unitary gauge in which we apply St$\ddot{u}$ckelberg trick in lowest dimensional EFT operators which are broken under time diffeomorphism. Particularly using this non-linear realization of broken time diffeomorphism and truncating the action by considering the contribution from two derivative terms in the metric we compute the two point and three point correlations from scalar perturbations and two point correlation from tensor perturbations to quantify the quantum fluctuations observed in Cosmic Microwave Background (CMB) map. We also use equilateral limit and squeezed limit configurations for the scalar three point correlations in Fourier space. To give future predictions from EFT setup and to check the consistency of our derived results for correlations, we use the results obtained from all class of canonical single field and general single field $P(X,\phi)$ model. This analysis helps us to fix the coefficients of the relevant operators in EFT in terms of the slow roll parameters and effective sound speed. Finally, using CMB observation from Planck we constrain all of these coefficients of EFT operators for single field slow roll inflationary paradigm.

[25] arXiv:1712.04261v2 [pdf, vox]

Identification of High Mass X-ray Binaries selected from XMM-Newton observations of the LMC

N. van Jaarsveld, D. A. H. Buckley, V. A. McBride, F. Haberl, G. Vasilopoulos, C. Maitra, A. Udalski, B. Miszalski
Submitted Wednesday 13 December 2017 @ 13:14:51 GMT

The Large Magellanic Cloud (LMC) currently hosts around 23 high mass X-ray binaries (HMXBs) of which most are Be/X-ray binaries. The LMC XMM-Newton survey provided follow-up observations of previously known X-ray sources that were likely HMXBs, as well as identifying new HMXB candidates. In total 19 candidate HMXBs were selected based on their X-ray hardness ratios. In this paper we present red and blue optical spectroscopy, obtained with SALT and the SAAO 1.9-m telescope, plus a timing analysis of the long term optical light curves from OGLE to confirm the nature of these candidates. We find that 9 of the candidates are new Be/X-ray Binaries, substantially increasing the LMC Be/X-ray binary population. Furthermore, we present the optical properties of these new systems, both individually and as a group of all the BeXBs identified by the XMM-Newton survey of the LMC.

[26] arXiv:1712.04750v1 [pdf, vox]

The Updated Multiple Star Catalog

Andrei Tokovinin
Submitted Wednesday 13 December 2017 @ 13:09:09 GMT
Accepted by ApJS. 11 pages, 9 figures, 6 tables. The catalog is available at http://www.ctio.noao​.edu/~atokovin/stars​/

The catalog of hierarchical stellar systems with three or more components is an update of the original 1997 version of the MSC. For two thousand hierarchies, the new MSC provides distances, component's masses and periods, as well as supplementary information (astrometry, photometry, identifiers, orbits, notes). The MSC content and format are explained, its incompleteness and strong observational selection are stressed. Nevertheless, the MSC can be used for statistical studies and it is a valuable source for planning observations of multiple stars. Rare classes of stellar hierarchies found in the MSC (with 6 or 7 components, extremely eccentric orbits, planar and possibly resonant orbits, hosting planets) are briefly presented. High-order hierarchies have smaller velocity dispersion compared to triples and are often associated with moving groups. The paper concludes by the analysis of the ratio of periods and separations between inner and outer subsystems. In wide hierarchies, the ratio of semimajor axes, estimated statistically, is distributed between 3 and 300, with no evidence of dynamically unstable systems.

[27] arXiv:1712.04735v1 [pdf, vox]

The evolution of young HII regions

P. D. Klaassen, K. G. Johnston, J. S. Urquhart, J. C. Mottram, T. Peters, R. Kuiper, H. Beuther, F. F. S. van der Tak, C. Goddi
Submitted Wednesday 13 December 2017 @ 12:30:33 GMT
Accepted for publication in A&A. 25 pages, 15 figures, 9 tables, with Table A.2 made available electronically via the CDS

High-mass stars form in much richer environments than those associated with isolated low-mass stars, and once they reach a certain mass, produce ionised (HII) regions. The formation of these pockets of ionised gas are unique to the formation of high-mass stars (M $>8$ M$_\odot$), and present an excellent opportunity to study the final stages of accretion, which could include accretion through the HII region itself. This study of the dynamics of the gas on both sides of these ionisation boundaries in very young HII regions aims to quantify the relationship between the HII regions and their immediate environments.We present high-resolution ($\sim$ 0.5$"$) ALMA observations of nine HII regions selected from the Red MSX Source (RMS) survey with compact radio emission and bolometric luminosities greater than 10$^4$ L$_\odot$. We focus on the initial presentation of the data, including initial results from the radio recombination line H29$\alpha$, some complementary molecules, and the 256 GHz continuum emission. Of the six (out of nine) regions with H29$\alpha$ detections, two appear to have cometary morphologies with velocity gradients across them, and two appear more spherical with velocity gradients suggestive of infalling ionised gas. The remaining two were either observed at low resolution or had signals that were too weak to draw robust conclusions. We also present a description of the interactions between the ionised and molecular gas (as traced by CS (J=5-4)), often (but not always) finding theHII region had cleared its immediate vicinity of molecules. Of our sample of nine, the observations of the two clusters expected to have the youngest HII regions (from previous radio observations) are suggestive of having infalling motions in the H29$\alpha$ emission, which could be indicative of late stage accretion onto the stars despite the presence of an HII region.

[28] arXiv:1712.04729v1 [pdf, vox]

Photometric study of three ultrashort-period contact binaries

L. Liu, S. -B., E. Fernandez Lajus, A. Essam, M. A. El-Sadek, X. Xiong
Submitted Wednesday 13 December 2017 @ 12:19:02 GMT
Accepted by Ap&SS

We carried out high-precision photometric observations of three eclipsing ultrashortperiod contact binaries (USPCBs). Theoretical models were fitted to the light-curves by means of the Wilson-Devinney code. The solutions suggest that the three targets have evolved to a contact phase. The photometric results are as follows: a) 1SWASP J030749.87-365201.7, q=0.439\pm0.003, f=0.0\pm3.6%; b) 1SWASP J213252.93-441822.6, q=0.560\pm0.003, f=14.2\pm1.9%; c) 1SWASP J200059.78+054408.9, q=0.436\pm0.008, f=58.4\pm1.8%. The light curves show O'Connell effects, which can be modeled by assumed cool spots. The cool spots models are strongly supported by the night-to-night variations in the I-band light curves of 1SWASP J030749.87-365201.7. For a comparative study, we collected the whole set of 28 well-studied USPCBs with P < 0.24 day. Thus, we found that most of them (17 of 28) are in shallow contact (i.e. fill-out factors f<20%). Only 4 USPCBs have deep fill-out factors (i.e. f>50%). Generally, contact binaries with deep fill-out factors are going to merge, but it is believed that USPCBs have just evolved to a contact phase. Hence, the deep USPCB 1SWASP J200059.78+054408.9 seems to be a contradiction, making it very interesting. Particularly, 1SWASP J030749.87-365201.7 is a zero contact binary within thermal equilibrium, implying that it should be a turn-off sample as predicted by the thermal relaxation oscillation (TRO) theory.

[29] arXiv:1712.04724v1 [pdf, vox]

Localization of transient gravitational wave sources: beyond triangulation

Stephen Fairhurst
Submitted Wednesday 13 December 2017 @ 12:06:41 GMT
27 pages, 7 figures

Rapid, accurate localization of gravitational wave transient events has proved critical to successful electromagnetic followup. In previous papers we have shown that localization estimates can be obtained through triangulation based on timing information at the detector sites. In practice, detailed parameter estimation routines use additional information and provide better localization than is possible based on timing information alone. In this paper, we extend the timing based localization approximation to incorporate consistency of observed signals with two gravitational wave polarizations, and an astrophysically motivated distribution of sources. Both of these provide significant improvements to source localization, allowing many sources to be restricted to a single sky region, with an area 40% smaller than predicted by timing information alone. Furthermore, we show that the vast majority of sources will be reconstructed to be circularly polarized or, equivalently, indistinguishable from face-on.

[30] arXiv:1712.04358v2 [pdf, vox]

A new mechanism of long-term period variations for W UMa-type contact binaries

Liang Liu, Shengbang Qian, Xiao Xiong
Submitted Wednesday 13 December 2017 @ 11:59:54 GMT
8 pages, 4 figures, accepted by MNRAS

W UMa-type contact binaries belong to close binary systems whose components exactly overflow their Roche lobes and share a common convective envelope (CCE). In the last twenty years, the long-term variations of their orbital periods have been thought to depend on several mechanisms. Now, we suggest a new mechanism: CCE-dominated mechanism. The CCE-dominated mechanism is found based on our numerical result, especially at high mass ratios, that the orbital periods (P) of contact binaries change very much with their fill-out factors (f). Because f is taken as a measurement of the thickness of CCE, the physical cause for the variation of P is a mass transfer between CCE and components. Further, an f-dominated simplification model for this mechanism is introduced. According to it, P may change in a long-term oscillation way with a similar time scale of the thermal modulation, meanwhile q is decreasing slowly till the two components merge. It could be also applied to explain the presence of extremely short period, high mass ratio and deep contact binaries. Moreover, the CCE-dominated mechanism should always work due to mass transfer and mass loss both occurring via CCE. Therefor, the effect of CCE on the variations of orbital periods may have been underestimated before.

[31] arXiv:1712.04715v1 [pdf, vox]

Quasar outflow energetics from broad absorption line variability

S. M. McGraw, J. C. Shields, F. W. Hamann, D. M. Capellupo, H. Herbst
Submitted Wednesday 13 December 2017 @ 11:35:46 GMT
19 pages, 3 figures, 4 tables, 1 supplementary figure, accepted to MNRAS

Quasar outflows have long been recognized as potential contributors to the co-evolution between supermassive black holes (SMBHs) and their host galaxies. The role of outflows in AGN feedback processes can be better understood by placing observational constraints on wind locations and kinetic energies. We utilize broad absorption line (BAL) variability to investigate the properties of a sample of 71 BAL quasars with P$\thinspace$V broad absorption. The presence of P$\thinspace$V BALs indicates that other BALs like C$\thinspace$IV are saturated, such that variability in those lines favours clouds crossing the line of sight. We use these constraints with measurements of BAL variability to estimate outflow locations and energetics. Our data set consists of multiple-epoch spectra from the Sloan Digital Sky Survey and MDM Observatory. We detect significant (4$\sigma$) BAL variations from 10 quasars in our sample over rest frame time-scales between < 0.2-3.8 yr. Our derived distances for the 10 variable outflows are nominally < 1-10 pc from the SMBH using the transverse-motion scenario, and < 100-1000 pc from the central source using ionization-change considerations. These distances, in combination with the estimated high outflow column densities (i.e. $N_{\textrm{H}}$ > 10$^{22}$ cm$^{-2}$), yield outflow kinetic luminosities between ~ 0.001-1 times the bolometric luminosity of the quasar, indicating that many absorber energies within our sample are viable for AGN feedback.

[32] arXiv:1712.04714v1 [pdf, vox]

Gaia DR1 evidence of disrupting Perseus Arm

Junichi Baba, Daisuke Kawata, Noriyuki Matsunaga, Robert J. J. Grand, Jason A. S. Hunt
Submitted Wednesday 13 December 2017 @ 11:33:42 GMT
5 pages. submitted to ApJ Letter

We have discovered a clear sign of the disruption phase of the Perseus arm in the Milky Way using Cepheid variables, taking advantage of the accurately measured distances of Cepheids and the proper motions from Gaia Data Release 1. Both the Galactocentric radial and rotation velocities of 77 Cepheids within 1.5 kpc of the Perseus arm are correlated with their distances from the Perseus arm, as the trailing side is rotating faster and moving inward compared to the leading side. We also found a negative vertex deviation for the Cepheids on the trailing side, $-27.6 \pm 2.4$ deg, in contrast to the positive vertex deviation in the solar neighborhood. This is, to our knowledge, the first direct evidence that the vertex deviation around the Perseus arm is affected by the spiral arm. We compared these observational trends with our $N$-body/hydrodynami​cs simulations based on a static density-wave spiral scenario and those based on a transient dynamic spiral scenario. Although our comparisons are limited to qualitative trends, they strongly favor a conclusion that the Perseus arm is in the disruption phase of a transient arm.

[33] arXiv:1712.04701v1 [pdf, vox]

Reconnection fluxes in eruptive and confined flares and implications for superflares on the Sun

Johannes Tschernitz, Astrid M. Veronig, Julia K. Thalmann, Jürgen Hinterreiter, Werner Pötzi
Submitted Wednesday 13 December 2017 @ 10:59:16 GMT
27 pages, 13 figures, 4 tables, accepted for publication in ApJ

We study the energy release process of a set of 51 flares (32 confined, 19 eruptive) ranging from GOES class B3 to X17. We use H$\alpha$ filtergrams from Kanzelh\"ohe Observatory together with SDO HMI and SOHO MDI magnetograms to derive magnetic reconnection fluxes and rates. The flare reconnection flux is strongly correlated with the peak of the GOES 1-8 \AA\ soft X-ray flux (c=0.92, in log-log space), both for confined and eruptive flares. Confined flares of a certain GOES class exhibit smaller ribbon areas but larger magnetic flux densities in the flare ribbons (by a factor of 2). In the largest events, up to $\approx$50\%\ of the magnetic flux of the active region (AR) causing the flare is involved in the flare magnetic reconnection. These findings allow us to extrapolate toward the largest solar flares possible. A complex solar AR hosting a magnetic flux of $2\cdot 10^{23}\, \mathrm{Mx}$, which is in line with the largest AR fluxes directly measured, is capable of producing an X80 flare, which corresponds to a bolometric energy of about $7 \cdot 10^{32}$ ergs. Using a magnetic flux estimate of $6\cdot 10^{23}\, \mathrm{Mx}$ for the largest solar AR observed, we find that flares of GOES class $\approx$X500 could be produced ($E_{\rm bol} \approx 3 \cdot 10^{33}$ ergs). These estimates suggest that the present day's Sun is capable of producing flares and related space weather events that may be more than an order of magnitude stronger than have been observed to date.

[34] arXiv:1712.04691v1 [pdf, vox]

Studying the transfer of magnetic helicity in solar active regions with the connectivity-based helicity flux density method

K. Dalmasse, E. Pariat, G. Valori, J. Jing, P. Démoulin
Submitted Wednesday 13 December 2017 @ 10:36:38 GMT
15 pages, 7 figures ; Accepted for publication in ApJ

In the solar corona, magnetic helicity slowly and continuously accumulates in response to plasma flows tangential to the photosphere and magnetic flux emergence through it. Analyzing this transfer of magnetic helicity is key for identifying its role in the dynamics of active regions (ARs). The connectivity-based helicity flux density method was recently developed for studying the 2D and 3D transfer of magnetic helicity in ARs. The method takes into account the 3D nature of magnetic helicity by explicitly using knowledge of the magnetic field connectivity, which allows it to faithfully track the photospheric flux of magnetic helicity. Because the magnetic field is not measured in the solar corona, modeled 3D solutions obtained from force-free magnetic field extrapolations must be used to derive the magnetic connectivity. Different extrapolation methods can lead to markedly different 3D magnetic field connectivities, thus questioning the reliability of the connectivity-based approach in observational applications. We address these concerns by applying this method to the isolated and internally complex AR 11158 with different magnetic field extrapolation models. We show that the connectivity-based calculations are robust to different extrapolation methods, in particular with regards to identifying regions of opposite magnetic helicity flux. We conclude that the connectivity-based approach can be reliably used in observational analyses and is a promising tool for studying the transfer of magnetic helicity in ARs and relate it to their flaring activity.

[35] arXiv:1712.04672v1 [pdf, vox]

Accurate photometry with digitized photographic plates of the Moscow collection

K. V. Sokolovsky, A. M. Zubareva, D. M. Kolesnikova, N. N. Samus, S. V. Antipin, A. A. Belinski
Submitted Wednesday 13 December 2017 @ 09:26:24 GMT
4 pages, 3 figures; proceedings of the IAU Symposium 339 Southern Horizons in Time-Domain Astronomy, 13-17 November 2017, Stellenbosch, South Africa

Photographic plate archives contain a wealth of information about positions and brightness celestial objects had decades ago. Plate digitization is necessary to make this information accessible, but extracting it is a technical challenge. We develop algorithms used to extract photometry with the accuracy of better than ~0.1m in the magnitude range 13<B<17 from photographic images obtained in 1948-1996 with the 40cm Sternberg institute's astrograph (30x30cm plate size, 10x10deg field of view) and digitized using a flatbed scanner. The extracted photographic lightcurves are used to identify thousands of new high-amplitude (>0.2m) variable stars. The algorithms are implemented in the free software VaST available at http://scan.sai.msu.​ru/vast/

[36] arXiv:1712.04654v1 [pdf, vox]

Modeling Radio Circular Polarization in the Crab Nebula

N. Bucciantini, B. Olmi
Submitted Wednesday 13 December 2017 @ 08:22:02 GMT
5 pages, 2 figures, accepted for publication in MNRAS

In this paper we present, for the first time, simulated maps of the circularly polarized synchrotron emission from the Crab nebula, using multidimensional state of the art models for the magnetic field geometry. Synchrotron emission is the signature of non-thermal emitting particles, typical of many high-energy astrophysical sources, both Galactic and extra-galactic ones. Its spectral and polarization properties allow us to infer key informations on the particles distribution function and magnetic field geometry. In recent years our understanding of pulsar wind nebulae has improved substantially thanks to a combination of observations and numerical models. A robust detection or non-detection of circular polarization will enable us to discriminate between an electron-proton plasma and a pair plasma, clarifying once for all the origin of the radio emitting particles, setting strong constraints on the pair production in pulsar magnetosphere, and the role of turbulence in the nebula. Previous attempts at measuring the circular polarization have only provided upper limits, but the lack of accurate estimates, based on reliable models, makes their interpretation ambiguous. We show here that those results are above the expected values, and that current polarimetric tecniques are not robust enough for conclusive result, suggesting that improvements in construction and calibration of next generation radio facilities are necessary to achieve the desired sensitivity.

[37] arXiv:1712.04645v1 [pdf, vox]

Chemical Abundances of Planetary Nebulae in the Substructures of M31 -- II. The Extended Sample and A Comparison Study with the Outer-disk Group

Xuan Fang, Ruben Garcia-Benito, Martin A. Guerrero, Yong Zhang, Xiaowei Liu, Christophe Morisset, Amanda I. Karakas, Marcelo M. Miller Bertolami, Haibo Yuan, Antonio Cabrera-Lavers
Submitted Wednesday 13 December 2017 @ 08:03:06 GMT
Accepted for publication in The Astrophysical Journal (ApJ); 33 pages including 20 figures and 9 tables

We report deep spectroscopy of ten planetary nebulae (PNe) in the Andromeda Galaxy (M31) using the 10.4m GTC. Our targets reside in different regions of M31, including halo streams and dwarf satellite M32, and kinematically deviate from the extended disk. The temperature-sensitiv​e [O III] 4363 auroral line is observed in all targets. For four PNe, the GTC spectra extend beyond 1 micron, enabling explicit detection of the [S III] 6312 and 9069,9531 lines and thus determination of the [S III] temperature. Abundance ratios are derived and generally consistent with AGB model predictions. Our PNe probably all evolved from low-mass (<2 M_sun) stars, as analyzed with the most up-to-date post-AGB evolutionary models, and their main-sequence ages are mostly ~2-5 Gyr. Compared to the underlying, smooth, metal-poor halo of M31, our targets are uniformly metal-rich ([O/H]> -0.4), and seem to resemble the younger population in the stream. We thus speculate that our halo PNe formed in the Giant Stream's progenitor through extended star formation. Alternatively, they might have formed from the same metal-rich gas as did the outer-disk PNe, but was displaced into their present locations as a result of galactic interactions. These interpretations are, although speculative, qualitatively in line with the current picture, as inferred from previous wide-field photometric surveys, that M31's halo is the result of complex interactions and merger processes. The behavior of N/O of the combined sample of the outer-disk and our halo/substructure PNe signifies that hot bottom burning might actually occur at <3 M_sun, but careful assessment is needed.

[38] arXiv:1712.04641v1 [pdf, vox]

Short Gamma-Ray Bursts and Gravitational-Wave Observations from Eccentric Compact Binaries

Wei-Wei Tan, Xi-Long Fan, F. Y. Wang
Submitted Wednesday 13 December 2017 @ 07:50:04 GMT
9 pages, 4 figures, 1 table, accepted by MNRAS

Mergers of compact binaries, such as binary neutron stars (BNSs), neutron star-black hole binaries (NSBHs), and binary black holes (BBHs), are expected to be the best candidates for the sources of gravitational waves (GWs) and the leading theoretical models for short gamma-ray bursts (SGRBs). Based on the observations of SGRBs, we could derive the merger rates of these compact binaries, and study the stochastic GW backgrounds (SGWBs) or the co-detection rates of GWs associate with SGRBs (GW-SGRBs). But before that, the most important thing is to derive the GW spectrum from a single GW source. Usually, GW spectrum from a circular orbit binary is assumed. However, observations of the large spatial offsets of SGRBs from their host galaxies imply that SGRB progenitors may be formed by the dynamical processes, and will merge with residual eccentricities. The orbital eccentricity has important effect on GW spectra, and therefore on the SGWB and GW-SGRB co-detection rate. Our results show that the power spectra of the SGWBs from eccentric compact binaries are greatly suppressed at low frequencies. Especially, SGWBs from binaries with high residual eccentricities will hard to be detected (above the detection frequency of $\sim100~\rm Hz$). For the co-detection rates of GW-SGRB events, they could be $\sim1.4$ times higher than the circular case within some particular ranges of $e_{\rm r}$ , but greatly reduced for high residual eccentricities (e.g., $e_{\rm r}>0.1$ for BNSs). In general, the BBH progenitors produce 200 and 10 times higher GW-SGRB events than the BNS and NSBH progenitors, respectively. Therefore, binaries with low residual eccentricities and high total masses will easier to be detected by aLIGO.

[39] arXiv:1712.04611v1 [pdf, vox]

Luminosity effect of O I 7771-5 triplet and atmospheric microturbulence in evolved A-, F-, and G-type stars

Yoichi Takeda, Gwanghui Jeong, Inwoo Han
Submitted Wednesday 13 December 2017 @ 05:13:45 GMT
20 pages, 10 figures and 3 tables along with 1 electronic data table (ancillary material), accepted for publication in Publ. Astron. Soc. Japan

It is known that the strength of neutral oxygen triplet lines at 7771-5 A shows a luminosity effect in evolved A through G stars. However, its general behavior across the HR diagram is not yet well understood, since the applicability limit of the relations proposed by various previous work (tending to be biased toward supergiants) still remains unclear. Besides, our understanding on the nature of atmospheric micro-scale turbulence, which is considered to play a significant role (along with the non-LTE line intensification) for the cause of this effect, is still insufficient. Towards clarifying these problems, we carried out an extensive non-LTE spectrum-fitting analysis of O I 7771--5 lines for unbiased sample of 75 evolved A-, F,- and G-type stars over wide luminosity classes (from subgiants through supergiants) including rapid rotators, from which the total equivalent width (W_77) was derived and the microturbulence (xi) was determined by two different (profile- and abundance-based) methods for each star. While we confirmed that W_77 tends to increase in the global sense as a star's absolute magnitude (M_V) becomes more luminous, distinctly different trends were found between lower-gravity (log g <~ 2.5) and higher-gravity (log g >~ 2.5) stars, in the sense that the M_V vs. W_77 formulas proposed by past studies are applicable only to the former supergiant group. In case of using W_77 for empirical M_V evaluation by such simple formulas, it is recommended to confine only to supergiants of -5 > M_V > -10. Regarding the microturbulence significantly controlling W_77, it roughly shows an increasing tendency with a decrease in surface gravity. However, the trend is not monotonic but rather intricate (e.g., hump, stagnation, or discontinuously large increase) depending on the stellar type and evolutionary stage.

[40] arXiv:1712.04606v1 [pdf, vox]

Disk-Driven Rotating Bipolar Outflow in Orion Source I

Tomoya Hirota, Masahiro N. Machida, Yuko Matsushita, Kazuhiro Motogi, Naoko Matsumoto, Mi Kyoung Kim, Ross A. Burns, Mareki Honma
Submitted Wednesday 13 December 2017 @ 04:30:14 GMT
16 pages, 8 figures. Accepted version of the manuscript before editing by Nature Astronomy. Published version is available on the SharedIt link; http://rdcu.be/AfTC

One of the outstanding problems in star-formation theory concerns the transfer of angular momentum such that mass can accrete onto a newly born young stellar object (YSO). From a theoretical standpoint, outflows and jets are predicted to play an essential role in angular momentum transfer and their rotation motions have been reported for both low- and high-mass YSOs. However, little quantitative discussion on outflow launching mechanisms have been presented for high-mass YSOs due to a lack of observational data. Here we present a clear signature of rotation in the bipolar outflow driven by Orion Source I, a high-mass YSO candidate, using the Atacama Large Millimeter/Submillim​eter Array (ALMA). A rotational transition of silicon monoxide (Si18O) reveals a velocity gradient perpendicular to the outflow axis which is consistent with that of the circumstellar disk traced by a high-excitation water (H2O) line. The launching radii and outward velocity of the outflow are estimated to be >10 au and 10 km s-1, respectively. These parameters rule out a possibility that the observed outflow is produced by entrainment of a high-velocity jet, and that contribution from stellar-wind or X-wind which have smaller launching radii are significant in the case of Source I. Thus, present results provide a convincing evidence of a rotating outflow directly driven by the magneto-centrifugal disk wind launched by a high-mass YSO candidate.

[41] arXiv:1712.04599v1 [pdf, vox]

Massive outflows associated with ATLASGAL clumps

Aiyuan Yang, Mark Thompson, James Urquhart, Wenwu Tian
Submitted Wednesday 13 December 2017 @ 03:32:26 GMT
27 pages, 12 figures, 10 tables, accepted by ApJS

We have undertaken the largest survey for outflows within the Galactic Plane using simultaneously observed 13CO and C18O data. 325 out of a total of 919 ATLASGAL clumps have data suitable to identify outflows, and 225 (69+-3%) of them show high velocity outflows. The clumps with detected outflows show significantly higher clump masses (M_{clump}), bolometric luminosities (L_{bol}), luminosity-to-mass ratios (L_{bol}/M_{clump}) and peak H_2 column densities (N_{H_2}) compared to those without outflows. Outflow activity has been detected within the youngest quiescent clump (i.e.,70um weak) in this sample and we find that the outflow detection rate increases with M_{clump},L_{bol},L_​{bol}/M_{clump} and N_{H_2},approaching 90% in some cases(uchii regions=93+-3%;maser​s=86+-4%;hchii regions=100%). This high detection rate suggests that outflows are ubiquitous phenomena of massive star formation. The mean outflow mass entrainment rate implies a mean accretion rate of ~10^{-4}M_\odot\,yr^​{-1}, in full agreement with the accretion rate predicted by theoretical models of massive star formation. Outflow properties are tightly correlated with M_{clump},L_{bol} and L_{bol}/M_{clump},an​d show the strongest relation with the bolometric clump luminosity. This suggests that outflows might be driven by the most massive and luminous source within the clump. The correlations are similar for both low-mass and high-mass outflows over 7 orders of magnitude, indicating that they may share a similar outflow mechanism. Outflow energy is comparable to the turbulent energy within the clump, however, we find no evidence that outflows increase the level of clump turbulence as the clumps evolve. This implies that the origin of turbulence within clumps is fixed before the onset of star formation.

[42] arXiv:1712.04597v1 [pdf, vox]

Bounds on Resonantly-Produced Sterile Neutrinos from Phase Space Densities of Milky Way Dwarf Galaxies

Mei-Yu Wang, John F. Cherry, Shunsaku Horiuchi, Louis E. Strigari
Submitted Wednesday 13 December 2017 @ 03:22:39 GMT
9 pages, 6 figures, 2 tables, to be submitted to PRD

We examine the bounds on resonantly-produced sterile neutrino dark matter from phase-space densities of Milky Way dwarf spheroidal galaxies (dSphs). The bounds result from a derivation of the dark matter coarse-grained phase-space density from the stellar kinematics, which allows us to explore bounds from some of the most compact dSphs without suffering the resolution limitation from N-body simulations that conventional methods have. We find that the strongest constraints come from very compact dSphs, such as Draco II and Segue 1. We additionally forecast the constraining power of a few dSph candidates that do not yet have associated stellar kinematic data, and show that they can improve the bounds if they are confirmed to be highly dark matter dominated systems. Our results demonstrate that compact dSphs provide important constraints on sterile neutrino dark matter that are comparable to other methods using as Milky Way satellite counts. In particular, if more compact systems are discovered from current or future surveys such as LSST or HSC, it should be possible to test models that explain the 3.5 keV X-ray line signal with a 7.1 keV sterile neutrino particle decay.

[43] arXiv:1712.04583v1 [pdf, vox]

CMB Spectral $μ$-Distortion of Multiple Inflation Scenario

Gimin Bae, Sungjae Bae, Seungho Choe, Seo Hyun Lee, Jungwon Lim, Heeseung Zoe
Submitted Wednesday 13 December 2017 @ 01:18:30 GMT
16 pages, 5 figures

In multiple inflation scenario having two inflations with an intermediate matter-dominated phase, the power spectrum is estimated to be enhanced on scales smaller than the horizon size at the beginning of the second inflation, $k > k_{\rm b}$. We require $k_{\rm b} > 10 {\rm Mpc}^{-1}$ to make sure that the enhanced power spectrum is consistent with large scale observation of cosmic microwave background (CMB). We consider the CMB spectral distortions generated by the dissipation of acoustic waves to constrain the power spectrum. The $\mu$-distortion value can be $10$ times larger than the expectation of the standard $\Lambda$CDM model ($\mu_{\Lambda\mathr​m{CDM}} \simeq 2 \times 10^{-8}$) for $ k_{\rm b} \lesssim 10^3 {\rm Mpc}^{-1}$, while the $y$-distortion is hardly affected by the enhancement of the power spectrum.

Submitted Tue, 12 Dec 2017

[44] arXiv:1712.04570v1 [pdf, vox]

Flare Activity of Wide Binary Stars with Kepler

Riley W. Clarke, James R. A. Davenport, Kevin R. Covey, Christoph Baranec
Submitted Tuesday 12 December 2017 @ 23:51:23 GMT
15 pages, 10 figures, accepted by ApJ

We present an analysis of flare activity in wide binary stars using a combination of value-added data sets from the NASA Kepler mission. The target list contains a set of previously discovered wide binary star systems identified by proper motions in the Kepler field. We cross-matched these systems with estimates of flare activity for $\sim$200,000 stars in the Kepler field, allowing us to compare relative flare luminosity between stars in coeval binaries. From a sample of 184 previously known wide binaries in the Kepler field, we find 58 with detectable flare activity in at least 1 component, 33 of which are similar in mass (q $>$ 0.8). Of these 33 equal-mass binaries, the majority display similar ($\pm 1$ dex) flare luminosity between both stars, as expected for stars of equal mass and age. However, we find two equal-mass pairs where the secondary (lower mass) star is more active than its counterpart, and two equal-mass pairs where the primary star is more active. The stellar rotation periods are also anomalously fast for stars with elevated flare activity. Pairs with discrepant rotation and activity qualitatively seem to have lower mass ratios. These outliers may be due to tidal spin-up, indicating these wide binaries could be hierarchical triple systems. We additionally present high resolution adaptive optics images for two wide binary systems to test this hypothesis. The demographics of stellar rotation and magnetic activity between stars in wide binaries may be useful indicators for discerning formation scenarios of these systems.

[45] arXiv:1712.04556v1 [pdf, vox]

Tracking Filament Evolution in the Low Solar Corona using Remote-Sensing and In-situ Observations

Manan Kocher, Enrico Landi, Susan T. Lepri
Submitted Tuesday 12 December 2017 @ 22:39:48 GMT
Submitted to ApJS

In the present work, we analyze a filament eruption associated with an ICME that arrived at L1 on August 5th, 2011. In multi-wavelength SDO/AIA images, three plasma parcels within the filament were tracked at high-cadence along the solar corona. A novel absorption diagnostic technique was applied to the filament material travelling along the three chosen trajectories to compute the column density and temperature evolution in time. Kinematics of the filamentary material were estimated using STEREO/EUVI and STEREO/COR1 observations. The Michigan Ionization Code used inputs of these density, temperature, and speed profiles for the computation of ionization profiles of the filament plasma. Based on these measurements we conclude the core plasma was in near ionization equilibrium, and the ionization states were not frozen-in at the altitudes where they were visible in absorption in AIA images. Additionally, we report that the filament plasma was heterogeneous, and the filamentary material was continuously heated as it expanded in the low solar corona.

[46] arXiv:1712.04540v1 [pdf, vox]

Herschel and ALMA Observations of Massive SZE-selected Clusters

John F. Wu, Paula Aguirre, Andrew J. Baker, Mark J. Devlin, Matt Hilton, John P. Hughes, Leopoldo Infante, Robert R. Lindner, Cristóbal Sifón
Submitted Tuesday 12 December 2017 @ 21:36:57 GMT
Accepted in ApJ, 46 pages, 13 figures

We present new Herschel observations of four massive, Sunyaev-Zel'dovich Effect (SZE)-selected clusters at $0.3 \leq z \leq 1.1$, two of which have also been observed with ALMA. We detect 19 Herschel/PACS counterparts to spectroscopically confirmed cluster members, five of which have redshifts determined via CO($4-3$) and [CI](${}^3P_1 - {}^3P_0$) lines. The mean [CI]/CO line ratio is $0.19 \pm 0.07$ in brightness temperature units, consistent with previous results for field samples. We do not detect significant stacked ALMA dust continuum or spectral line emission, implying upper limits on mean interstellar medium (H$_2$ + HI) and molecular gas masses. An apparent anticorrelation of $L_{IR}$ with clustercentric radius is driven by the tight relation between star formation rate and stellar mass. We find average specific star formation rate log(sSFR/yr$^{-1}$) = -10.36, which is below the SFR$-M_*$ correlation measured for field galaxies at similar redshifts. The fraction of infrared-bright galaxies (IRBGs; $\log (L_{IR}/L_\odot) > 10.6$) per cluster and average sSFR rise significantly with redshift. For CO detections, we find $f_{gas} \sim 0.2$, comparable to those of field galaxies, and gas depletion timescales of about 2 Gyr. We use radio observations to distinguish active galactic nuclei (AGNs) from star-forming galaxies. At least four of our 19 Herschel cluster members have $q_{IR} < 1.8$, implying an AGN fraction $f_{AGN} \gtrsim 0.2$ for our PACS-selected sample.

[47] arXiv:1712.04515v1 [pdf, vox]

New Distances to Four Supernova Remnants

S. Ranasinghe, D. A. Leahy, Wenwu Tian
Submitted Tuesday 12 December 2017 @ 20:58:35 GMT
9 pages, 12 figures

Distances are found for four supernova remnants SNRs without previous distance measurements. HI spectra and HI channel maps are used to determine the maximum velocity of HI absorption for four supernova remnants (SNRs). We examined $^{13}$CO emission spectra and channel maps to look for possible molecular gas associated with each SNR, but did not find any. The resulting distances for the SNRs are $3.5 \pm 0.2$ kpc (G$24.7+0.6$), $4.7 \pm 0.3$ kpc (G$29.6+0.1$) , $ 4.1 \pm 0.5$ kpc (G$41.5+0.4$) and $4.5\pm 0.4 - 9.0 \pm 0.4$ kpc (G$57.2+0.8$).

[48] arXiv:1712.04512v1 [pdf, vox]

COLOSSUS: A python toolkit for cosmology, large-scale structure, and dark matter halos

Benedikt Diemer
Submitted Tuesday 12 December 2017 @ 20:57:28 GMT
12 pages, 6 figures. Comments and suggestions welcome. Code available at https://bitbucket.or​g/bdiemer/colossus

This paper introduces Colossus, a public, open-source python package for calculations related to cosmology, the large-scale structure of matter in the universe, and the properties of dark matter halos. The code is designed to be fast and easy to use, with a coherent, well-documented user interface. The cosmology module implements FLRW cosmologies including curvature, relativistic species, and different dark energy equations of state, and provides fast computations of the linear matter power spectrum, variance, and correlation function. The large-scale structure module is concerned with the properties of peaks in Gaussian random fields and halos in a statistical sense, including their peak height, peak curvature, halo bias, and mass function. The halo module deals with spherical overdensity radii and masses, density profiles, concentration, and the splashback radius. To facilitate the rapid exploration of these quantities, Colossus implements about 40 different fitting functions from the literature. I discuss the core routines in detail, with a particular emphasis on their accuracy. Colossus is available at bitbucket.org/bdieme​r/colossus.

[49] arXiv:1712.04510v1 [pdf, vox]

A new holographic dark energy model in Brans-Dicke theory with logarithmic scalar field

Ehsan Sadri, Babak Vakili
Submitted Tuesday 12 December 2017 @ 20:52:03 GMT
13 pages, 7 figures, 1 table, to appear in: Astrophys. Space Sci

We study a holographic dark energy model in the framework of Brans-Dicke (BD) theory with taking into account the interaction between dark matter and holographic dark energy. We use the recent observational data sets, namely SN Ia compressed Joint Light-Analysis(cJLA) compilation, Baryon Acoustic Oscillations (BAO) from BOSS DR12 and the Cosmic Microwave Background (CMB) of Planck 2015. After calculating the evolution of the equation of state as well as the deceleration parameters, we find that with a logarithmic form for the BD scalar field the phantom crossing can be achieved in the late time of cosmic evolution. Unlike the conventional theory of holographic dark energy in standard cosmology ($\omega_D=0$), our model results a late time accelerated expansion. It is also shown that the cosmic coincidence problem may be resolved in the proposed model. We execute the statefinder and Om diagnostic tools and demonstrate that interaction term does not play a significant role. Based on the observational data sets used in this paper it seems that the best value with $1\sigma$ and $2\sigma$ confidence interval are $\Omega_m=0.268^{+0.​008~+0.010}_{-0.007~​-0.009}$, $ \alpha=3.361^{+0.332​~+0.483}_{-0.401~-0.​522}$, $\beta=5.560^{+0.541​~+0.780}_{-0.510~-0.​729}$, $c=0.777^{+0.023~+0.​029}_{-0.017~-0.023}​$ and $b^2 =0.045$, according to which we find that the proposed model in the presence of interaction is compatible with the recent observational data.

[50] arXiv:1712.04505v1 [pdf, vox]

Molecular outflow and feedback in the obscured Quasar XID2028 revealed by ALMA

M. Brusa, G. Cresci, E. Daddi, R. Paladino, M. Perna, A. Bongiorno, E. Lusso, M. T. Sargent, V. Casasola, C. Feruglio, F. Fraternali, I. Georgiev, V. Mainieri, S. Carniani, A. Comastri, F. Duras, F. Fiore, F. Mannucci, A. Marconi, E. Piconcelli, G. Zamorani, R. Gilli, F. La Franca, G. Lanzuisi, D. Lutz, P. Santini, N. Z. Scoville, C. Vignali, F. Vito, S. Rabien, L. Busoni, M. Bonaglia
Submitted Tuesday 12 December 2017 @ 20:37:43 GMT
15 pages, 11 figures (including Appendix). Accepted for publication on A&A

We imaged with ALMA and ARGOS/LUCI the molecular gas and the dust and stellar continuum in XID2028, an obscured QSO at z=1.593, where the presence of a massive outflow in the ionized gas component traced by the [O III]5007 emission has been resolved up to 10 kpc. This target represents a unique test case to study QSO 'feedback in action' at the peak epoch of AGN-galaxy coevolution. The QSO has been detected in the CO(5-4) transition and in the 1.3mm continuum, at ~30 and ~20 {\sigma} significance respectively, with both emissions confined in the central (<4 kpc) radius area. Our analysis suggests the presence of a fast rotating molecular disc (v~400 km/s) on very compact scales, and well inside the galaxy extent seen in the rest-frame optical light (~10 kpc, as inferred from the LUCI data). Adding available measurements in additional two CO transitions, CO(2-1) and CO(3-2), we could derive a total gas mass of ~10$^{10}$ M$_\odot$, thanks to a critical assessment of CO excitation and the comparison with Rayleigh-Jeans continuum estimate. This translates into a very low gas fraction (<5%) and depletion time scales of 40-75 Myr, reinforcing the result of atypical gas consumption conditions in XID2028, possibly due to feedback effects on the host galaxy. Finally, we also detect at ~5{\sigma} the presence of high velocity CO gas, which we interpret as a signature of galaxy-scale molecular outflow, spatially coincident with the ionised gas outflow. XID2028 represents therefore a unique case where the measurement of total outflowing mass (~500-800 M$_\odot$/yr) including the molecular and atomic components, in both the ionised and neutral phases, has been attempted for a high-z QSO.

[51] arXiv:1712.04500v1 [pdf, vox]

A view of the H-band light-element chemical patterns in Globular Clusters under the AGB self-enrichment scenario

F. Dell'Agli, D. A. García-Hernández, P. Ventura, S. Mészáros, T. Masseron, J. G. Fernández-Trincado, B. Tang, M. Shetrone, O. Zamora, S. Lucatello
Submitted Tuesday 12 December 2017 @ 20:29:58 GMT
22 pages and 11 figures; accepted for publication in MNRAS

We discuss the self-enrichment scenario by AGB stars for the formation of multiple populations in globular clusters (GCs) by analyzing data set of giant stars observed in 9 Galactic GCs, covering a wide range of metallicities and for which the simultaneous measurements of C, N, O, Mg, Al, Si are available. To this aim we calculated 6 sets of AGB models, with the same chemical composition as the stars belonging to the first generation of each GC. We find that the AGB yields can reproduce the set of observations available, not only in terms of the degree of contamination shown by stars in each GC but, more important, also the observed trend with metallicity, which agrees well with the predictions from AGB evolution modelling. While further observational evidences are required to definitively fix the main actors in the pollution of the interstellar medium from which new generation of stars formed in GCs, the present results confirm that the gas ejected by stars of mass in the range $4~\rm M_{\odot} \leq \rm M \leq 8~\rm M_{\odot}$ during the AGB phase share the same chemical patterns traced by stars in GCs.

[52] arXiv:1712.04492v1 [pdf, vox]

Super-luminous Type II supernovae powered by magnetars

Luc Dessart, Edouard Audit
Submitted Tuesday 12 December 2017 @ 20:12:44 GMT
submitted to A&A on 2 Nov 2017

Magnetar power is believed to be at the origin of numerous super-luminous supernovae (SNe) of Type Ic, arising from compact, hydrogen-deficient, Wolf-Rayet type stars. Here, we investigate the properties that magnetar power would have on standard-energy SNe associated with 15-20Msun blue or red supergiant (BSG/RSG) stars. We use a combination of Eulerian grey radiation-hydrodynam​ics and non-LTE steady-state radiative transfer to study their dynamical, photometric, and spectroscopic properties. Adopting magnetar fields of 1, 3.5, 7 x 10^14G and rotational energies of 0.4, 1, and 3 x 10^51erg, we produce bolometric light curves with a broad maximum covering 50-150d and a magnitude of 10^43-10^44erg/s. The spectra at maximum light are analogous to those of standard SNe II-P but bluer. Although the magnetar energy is channelled roughly in equal proportion between SN kinetic energy and SN luminosity, the latter may be boosted by a factor 10-100 compared to a standard SN II. This influence breaks the observed relation between brightness and expansion rate of standard Type II SNe. Magnetar energy injection also delays recombination and may even cause re-ionization, with a reversal in photospheric temperature and velocity. Depositing the magnetar energy in a narrow mass shell at the ejecta base leads to the formation of a dense shell at a few 1000km/s, which causes a light-curve bump at the end of the photospheric phase. Depositing this energy over a broad range of mass in the inner ejecta, to mimic the effect of multi-dimensional fluid instabilities, prevents the formation of a dense shell and produces an earlier-rising and smoother light curve. The magnetar influence on the SN radiation is generally not visible prior to 20-30d, during which one may discern a BSG from a RSG progenitor. We propose a magnetar model for the super-luminous Type II SN OGLE-SN14-073.

[53] arXiv:1712.04490v1 [pdf, vox]

SPIRou Input Catalogue: Global properties of 440 M dwarfs observed with ESPaDOnS at CFHT

Pascal Fouqué, Claire Moutou, Lison Malo, Eder Martioli, Olivia Lim, Arvind Rajpurohit, Etienne Artigau, Xavier Delfosse, Jean-François Donati, Thierry Forveille, Julien Morin, France Allard, Raphaël Delage, René Doyon, Elodie Hébrard, Vasco Neves
Submitted Tuesday 12 December 2017 @ 20:05:23 GMT
34 pages, 12 figures, 13 tables, MNRAS in press December 11, 2017

Present and future high-precision radial-velocity spectrometers dedicated to the discovery of low-mass planets orbiting low-mass dwarfs need to focus on the best selected stars to make an efficient use of telescope time. In the framework of the preparation of the SPIRou Input Catalog, the CoolSnap program aims at screening M dwarfs in the solar neighborhood against binarity, rapid rotation, activity, ... To optimize the selection, the present paper describes the methods used to compute effective temperature, metallicity, projected rotation velocity of a large sample of 440 M dwarfs observed in the visible with the high-resolution spectro-polarimeter ESPaDOnS at CFHT. It also summarizes known and newly-discovered spectroscopic binaries, and stars known to belong to visual multiple systems. A calibration of the projected rotation velocity versus measured line widths for M dwarfs observed by the ESPaDOnS spectro-polarimeter is derived, and the resulting values are compared to equatorial rotation velocities deduced from rotation periods and radii. A comparison of the derived effective temperatures and metallicities with literature values is also conducted. Finally, the radial velocity uncertainty of each star in the sample is estimated, to narrow down the selection of stars to be included into the SPIRou Input Catalogue (SPIC).

[54] arXiv:1712.04486v1 [pdf, vox]

Transparency of 2 μm window of Titan's atmosphere

Pascal Rannou, Benoît Seignovert, Stéphane Le Mouélic, Lucas Maltagliati, Micheal Rey, Christophe Sotin
Submitted Tuesday 12 December 2017 @ 19:48:45 GMT

Titan's atmosphere is optically thick and hides the surface and the lower layers from the view at almost all wavelengths. However, because gaseous absorptions are spectrally selective, some narrow spectral intervals are relatively transparent and allow to probe the surface. To use these intervals (called windows) a good knowledge of atmospheric absorption is necessary. Once gas spectroscopic linelists are well established, the absorption inside windows depends on the way the far wings of the methane absorption lines are cut-off. We know that the intensity in all the windows can be explained with the same cut-off parameters, except for the window at 2 {\mu}m. This discrepancy is generally treated with a workaround which consists in using a different cut-off description for this specific window. This window is relatively transparent and surface may have specific spectral signatures that could be detected. Thus, a good knowledge of atmosphere opacities is essential and our scope is to better understand what causes the difference between the 2 {\mu}m window and the other windows. In this work, we used scattered light at the limb and transmissions in occultation observed with VIMS (Visual Infrared Mapping Spectrometer) onboard Cassini, around the 2 {\mu}m window. Data shows an absorption feature that participates to the shape of this window. Our atmospheric model fits well the VIMS data at 2 {\mu}m with the same cut-off than for the other windows, provided an additional absorption is introduced in the middle of the window around ~2.065 {\mu}m. It explains well the discrepancy between the cut-off used at 2 {\mu}m, and we show that a gas with a fairly constant mixing ratio, possibly ethane, may be the cause of this absorption. Finally, we studied the impact of this absorption on the retrieval of the surface reflectivity and found that it is significant.

[55] arXiv:1712.04483v1 [pdf, vox]

A Candidate Transit Event around Proxima Centauri

Yiting Li, Gudmundur Stefansson, Paul Robertson, Andrew Monson, Caleb Canas, Suvrath Mahadevan
Submitted Tuesday 12 December 2017 @ 19:44:26 GMT
3 pages, 1 figure. Accepted for publication in Research Notes of the AAS

We present a single candidate transit event around Proxima Centauri, found during a blind transit search using a robotic 30\,cm telescope at Las Campanas Observatory. The event lasted 1 hour, with an estimated depth of 5\,mmag, and is inconsistent with the transit window predicted for the recently discovered planet b. We modeled the lightcurve under the assumption that the event was caused by a transiting exoplanet, and our model predicts the planet has a radius $R \sim 1 R_{\oplus}$. We encourage continued monitoring of Proxima to elucidate the origin of this event.

[56] arXiv:1712.04476v1 [pdf, vox]

Photometric redshifts for the next generation of deep radio continuum surveys - II. Gaussian processes and hybrid estimates

Kenneth J Duncan, Matt J. Jarvis, Michael J. I. Brown, Huub J. A. Rottgering
Submitted Tuesday 12 December 2017 @ 19:17:08 GMT
13 pages, 12 figures. Submitted for publication in MNRAS

Building on the first paper in this series (Duncan et al. 2018), we present a study investigating the performance of Gaussian process photometric redshift (photo-z) estimates for galaxies and active galactic nuclei detected in deep radio continuum surveys. A Gaussian process redshift code is used to produce photo-z estimates targeting specific subsets of both the AGN population - infrared, X-ray and optically selected AGN - and the general galaxy population. The new estimates for the AGN population are found to perform significantly better at z > 1 than the template-based photo-z estimates presented in our previous study. Our new photo-z estimates are then combined with template estimates through hierarchical Bayesian combination to produce a hybrid consensus estimate that outperforms either of the individual methods across all source types. Photo-z estimates for radio sources that are X-ray sources or optical/IR AGN are signficantly improved in comparison to previous template-only estimates, with outlier fractions and robust scatter reduced by up to a factor of ~4. The ability of our method to combine the strengths of the two input photo-z techniques and the large improvements we observe illustrate its potential for enabling future exploitation of deep radio continuum surveys for both the study of galaxy and black hole co-evolution and for cosmological studies.

[57] arXiv:1712.04469v1 [pdf, vox]

Halo models of HI selected galaxies

Niladri Paul, Tirthankar Roy Choudhury, Aseem Paranjape
Submitted Tuesday 12 December 2017 @ 19:03:22 GMT
17 pages, 16 figures

Modelling the distribution of neutral hydrogen (HI) in dark matter halos is important for studying galaxy evolution in the cosmological context. We compute the abundance and clustering properties of HI-selected galaxies using halo models constrained by data from the ALFALFA survey. We apply an MCMC-based statistical analysis to constrain the model parameters through two different approaches. In the first approach, we describe the HI content of galaxies in dark matter halos directly, using a halo occupation distribution (HOD) for the number counts of HI galaxies. We find that a significant number of low mass ($m_{\rm HI} \lesssim 10^{9.5} M_{\odot}$) galaxies must be satellites. In the second, more novel approach, we infer the HI-dark matter connection at the massive end ($m_{\rm HI} > 10^{9.5} M_{\odot}$) $\textit{indirectly}​$, using optical properties of low-redshift galaxies as an intermediary. In particular, we use a previously calibrated optical HOD describing the luminosity- and colour-dependent clustering of SDSS galaxies and describe the HI content using a statistical scaling relation between the optical properties and HI mass. The resulting best-fit scaling relation identifies massive HI galaxies primarily with optically faint blue centrals, consistent with expectations from galaxy formation models. Our results will be useful in making forecasts for future observations of HI galaxies with upcoming radio telescopes like the SKA, as well as in exploring synergies between SKA and optical surveys such as Euclid and LSST.

[58] arXiv:1712.04467v1 [pdf, vox]

Modeling the Impact of Baryons on Subhalo Populations with Machine Learning

Ethan O. Nadler, Yao-Yuan Mao, Risa H. Wechsler, Shea Garrison-Kimmel, Andrew Wetzel
Submitted Tuesday 12 December 2017 @ 19:02:05 GMT
20 pages, 14 figures, submitted to ApJ

We identify subhalos in dark matter only (DMO) zoom-in simulations that are likely to be disrupted due to baryonic effects by using a random forest classifier trained on two hydrodynamic simulations of Milky Way-mass host halos from the Latte suite of the Feedback in Realistic Environments (FIRE) project. We train our classifier using five properties of each disrupted and surviving subhalo: pericentric distance and scale factor at first pericentric passage after accretion, and scale factor, virial mass, and maximum circular velocity at accretion. Our five-property classifier identifies disrupted subhalos in the FIRE simulations with $95\%$ accuracy. We predict surviving subhalo populations in DMO simulations of the FIRE host halos, finding excellent agreement with the hydrodynamic results; in particular, our classifier outperforms DMO zoom-in simulations that include the gravitational potential of the central galactic disk in each hydrodynamic simulation, indicating that it captures both the dynamical effects of a central disk and additional baryonic physics. We also predict surviving subhalo populations for a suite of DMO zoom-in simulations of MW-mass host halos, finding that baryons impact each system consistently and that the predicted amount of subhalo disruption is larger than the host-to-host scatter among the subhalo populations. Although the small size and specific baryonic physics prescription of our training set limits the generality of our results, our work suggests that machine learning classification algorithms trained on hydrodynamic zoom-in simulations can efficiently predict realistic subhalo populations.

[59] arXiv:1712.04464v1 [pdf, vox]

SCORCH. II. Radiation-Hydrodynam​ic simulations of reionization with varying radiation escape fractions

Aristide Doussot, Hy Trac, Renyue Cen
Submitted Tuesday 12 December 2017 @ 19:00:43 GMT
12 pages, 11 figures, 3 tables, submitted to ApJ

For the Simulations and Constructions of the Reionization of Cosmic Hydrogen (SCORCH) project, we present new radiation-hydrodynam​ic simulations with updated high-redshift galaxy populations and varying radiation escape fractions. The simulations are designed to have fixed Thomson optical depth $\tau \approx 0.06$, consistent with recent Planck observations, and similar midpoint of reionization at $z \approx 7.5$, but with different ionization histories. The modeled galaxy luminosity functions and ionizing photon production rates are in good agreement with recent HST observations. Adopting a power-law form for the radiation escape fraction $f_{\text{esc}}(z) = f_8[(1+z)/9]^{a_8}$, we simulate the cases for $a_8 = 0$, 1, 2 and find that $a_8 \lesssim 2$ in order to have reionization end in the range $5.5 \lesssim z \lesssim 6.5$, consistent with Lyman alpha forest observations. At fixed $\tau$ and as the power-law slope $a_8$ increases, the reionization process starts relatively earlier, ends relatively later, and the duration $\Delta z$ increases and the asymmetry $Az$ decreases. We find a range of durations $3.1 \lesssim \Delta z \lesssim 3.8$ that is currently in tension with the upper limit $\Delta z < 2.8$ inferred from a recent joint analysis of Planck and South Pole Telescope observations.

[60] arXiv:1712.04462v1 [pdf, vox]

Online radio interferometric imaging: assimilating and discarding visibilities on arrival

Xiaohao Cai, Luke Pratley, Jason D. McEwen
Submitted Tuesday 12 December 2017 @ 19:00:22 GMT
14 pages, 5 figures

The emerging generation of radio interferometric (RI) telescopes, such as the Square Kilometre Array (SKA), will acquire massive volumes of data and transition radio astronomy to a big-data era. The ill-posed inverse problem of imaging the raw visibilities acquired by RI telescopes will become significantly more computationally challenging, particularly in terms of data storage and computational cost. Current RI imaging methods, such as CLEAN, its variants, and compressive sensing approaches (sparse regularisation), have yielded excellent reconstruction fidelity. However, scaling these methods to big-data remains difficult if not impossible in some cases. All state-of-the-art methods in RI imaging lack the ability to process data streams as they are acquired during the data observation stage. Such approaches are referred to as online processing methods. We present an online sparse regularisation methodology for RI imaging. Image reconstruction is performed simultaneously with data acquisition, where observed visibilities are assimilated into the reconstructed image as they arrive and then discarded. Since visibilities are processed online, good reconstructions are recovered much faster than standard (offline) methods which cannot start until the data acquisition stage completes. Moreover, the online method provides additional computational savings and, most importantly, dramatically reduces data storage requirements. Theoretically, the reconstructed images are of the same fidelity as those recovered by the equivalent offline approach and, in practice, very similar reconstruction fidelity is achieved. We anticipate online imaging techniques, as proposed here, will be critical in scaling RI imaging to the emerging big-data era of radio astronomy.

[61] arXiv:1712.04461v1 [pdf, vox]

Analytic Derivation of the Halo Mass Function from the Non-Linear Cosmic Density Field

Laila Linke, Johannes Schwinn, Matthias Bartelmann
Submitted Tuesday 12 December 2017 @ 19:00:16 GMT
7 pages, 8 figures, submitted to MNRAS

We estimate the halo mass function (HMF) by applying the excursion set approach to the non-linear cosmic density field. Thereby, we account for the non-Gaussianity of today's density distribution and constrain the HMF independent of the linear collapse threshold $\delta_{\textrm{cri​t}}$. We consider a spherical region as a halo, if its density today exceeds the virial overdensity threshold $\Delta$. We model the probability distribution of the non-linear density field by a superposition of a Gaussian and a lognormal distribution, which we constrain with the bispectrum of density fluctuations, predicted by the kinetic field theory description of cosmic structure formation. Two different excursion set approaches are compared. The first treats the density $\delta$ as an uncorrelated random walk of the smoothing scale $R$. The second assumes $\delta(R)$ to be correlated. We find that the resulting HMFs correspond well to the HMF found in numerical simulations if the correlation of $\delta(R)$ is taken into account. Furthermore, the HMF depends only weakly on the choice of the density threshold $\Delta$.

[62] arXiv:1712.04460v1 [pdf, vox]

VALES: IV. Exploring the transition of star formation efficiencies between normal and starburst galaxies using APEX/SEPIA Band-5 and ALMA at low redshift

C. Cheng, E. Ibar, T. M. Hughes, V. Villanueva, R. Leiton, G. Orellana, A. Munoz-Arancibia, N. Lu, C. K. Xu, C. N. A. Willmer, J. Huang, T. Cao, C. Yang, Y. Q. Xue, K. Torstensson
Submitted Tuesday 12 December 2017 @ 19:00:08 GMT
9pages, 7 figures, 1 table, accepted for publication in MNRAS

In this work we present new APEX/SEPIA Band-5 observations targeting the CO ($J=2\text{-}1$) emission line of 24 Herschel-detected galaxies at $z=0.1-0.2$. Combining this sample {with} our recent new Valpara\'iso ALMA Line Emission Survey (VALES), we investigate the star formation efficiencies (SFEs = SFR/$M_{\rm H_{2}}$) of galaxies at low redshift. We find the SFE of our sample bridges the gap between normal star-forming galaxies and Ultra-Luminous Infrared Galaxies (ULIRGs), which are thought to be triggered by different star formation modes. Considering the $\rm SFE'$ as the SFR and the $L'_{\rm CO}$ ratio, our data show a continuous and smooth increment as a function of infrared luminosity (or star formation rate) with a scatter about 0.5 dex, instead of a steep jump with a bimodal behaviour. This result is due to the use of a sample with a much larger range of sSFR/sSFR$_{\rm ms}$ using LIRGs, with luminosities covering the range between normal and ULIRGs. We conclude that the main parameters controlling the scatter of the SFE in star-forming galaxies are the systematic uncertainty of the $\alpha_{\rm CO}$ conversion factor, the gas fraction and physical size.

[63] arXiv:1712.04454v1 [pdf, vox]

Robo-AO Kepler Survey IV: the effect of nearby stars on 3857 planetary candidate systems

Carl Ziegler, Nicholas M. Law, Christoph Baranec, Reed Riddle, Dmitry A. Duev, Ward Howard, Rebecca Jensen-Clem, S. R. Kulkarni, Maïssa Salama
Submitted Tuesday 12 December 2017 @ 19:00:02 GMT
Submitted to AAS Journals

We present the overall statistical results from the Robo-AO Kepler planetary candidate survey, comprising of 3857 observations with 0.1"-resolution of planetary candidate systems with Robo-AO, an automated laser adaptive optics system. These observations reveal previously unknown nearby stars blended with the planetary candidate host star which alter the derived planetary radii or may be the source of an astrophysical false positive transit signal. In the first three papers in the survey, we detected 440 nearby stars around 3313 planetary candidate host stars. In this paper, we present observations of 532 planetary candidate host stars, detecting 94 companions around 88 stars; 84 of these companions have not previously been observed in high-resolution. We also report 50 more-widely-separate​d companions near 715 targets previously observed by Robo-AO. We derive corrected planetary radius estimates for the 814 planetary candidates in systems with a detected nearby star. If planetary candidates are equally likely to orbit the primary or secondary star, the radius estimates for planetary candidates in systems with likely bound nearby stars increase by a factor of 1.54, on average. We find that 35 previously-believed rocky planet candidates are likely not rocky due to the presence of nearby stars. From the combined datasets from the complete Robo-AO KOI survey, we find that 14.5\pm0.5% of planetary candidate hosts have a nearby star with 4", while 1.2% have two nearby stars and 0.08% have three. We find that 16% of Earth-sized, 13% of Neptune-sized, 14% of Saturn-sized, and 19% of Jupiter-sized planet candidates have stars close enough to affect their radius estimates.

[64] arXiv:1712.04455v1 [pdf, vox]

Detection of long nulls in PSR B1706$-$16, a pulsar with large timing irregularities

Arun Naidu, Bhal Chandra Joshi, P. K Manoharan, M. A Krishnakumar
Submitted Tuesday 12 December 2017 @ 19:00:02 GMT
Accepted for publication in MNRAS

Single pulse observations, characterizing in detail, the nulling behaviour of PSR B1706$-$16 are being reported for the first time in this paper. Our regular long duration monitoring of this pulsar reveals long nulls of 2 to 5 hours with an overall nulling fraction of 31$\pm$2\%. The pulsar shows two distinct phases of emission. It is usually in an active phase, characterized by pulsations interspersed with shorter nulls, with a nulling fraction of about 15 \%, but it also rarely switches to an inactive phase, consisting of long nulls. The nulls in this pulsar are concurrent between 326.5 and 610 MHz. Profile mode changes accompanied by changes in fluctuation properties are seen in this pulsar, which switches from mode A before a null to mode B after the null. The distribution of null durations in this pulsar is bimodal. With its occasional long nulls, PSR B1706$-$16 joins the small group of intermediate nullers, which lie between the classical nullers and the intermittent pulsars. Similar to other intermediate nullers, PSR B1706$-$16 shows high timing noise, which could be due to its rare long nulls if one assumes that the slowdown rate during such nulls is different from that during the bursts.

[65] arXiv:1712.04449v1 [pdf, vox]

Isotropic-Nematic Phase Transitions in Gravitational Systems II: Higher Order Multipoles

Ádám Takács, Bence Kocsis
Submitted Tuesday 12 December 2017 @ 19:00:01 GMT
7 pages, 5 figures, submitted to ApJL

The gravitational interaction among bodies orbiting in a spherical potential leads to the rapid relaxation of the orbital planes' distribution, a process called vector resonant relaxation. We examine the statistical equilibrium of this process for a system of bodies with similar semimajor axes and eccentricities. We extend the previous model of Roupas, Kocsis, and Tremaine (2017), by accounting for the multipole moments beyond the quadrupole, which dominate the interaction for radially overlapping orbits. Nevertheless, we find no qualitative differences between the behavior of the system with respect to the model restricted to the quadrupole interaction. The equilibrium distribution resembles a counterrotating disk at low temperature and a spherical structure at high temperature. The system exhibits a first order phase transition between the disk and the spherical phase in the canonical ensemble if the total angular momentum is below a critical value. We find that the phase transition erases the high order multipoles, i.e. small-scale structure most efficiently. The small residual anisotropies are dominated by the quadrupole in the disordered phase. The system admits a maximum entropy and a maximum energy, which lead to the existence of negative temperature equilibria.

[66] arXiv:1712.04450v1 [pdf, vox]

On the Origin of Diffuse Ionized Gas in the Antennae Galaxy

Peter M. Weilbacher, Ana Monreal-Ibero, Anne Verhamme, Christer Sandin, Matthias Steinmetz, Wolfram Kollatschny, Davor Krajnović, Sebastian Kamann, Martin M. Roth, Santiago Erroz-Ferrer, Raffaella Anna Marino, Michael V. Maseda, Martin Wendt, Roland Bacon, Stefan Dreizler, Johan Richard, Lutz Wisotzki
Submitted Tuesday 12 December 2017 @ 19:00:01 GMT
Paper resubmitted to A&A after modifications following advice of the referee. Data available at http://muse-vlt.eu/s​cience/antennae/

The "Antennae Galaxy" (NGC 4038/39) is the closest major interacting galaxy system and therefore often taken as merger prototype. We present the first comprehensive integral field spectroscopic dataset of this system, observed with the MUSE instrument at the ESO VLT. We cover the two regions in this system which exhibit recent star-formation: the central galaxy interaction and a region near the tip of the southern tidal tail. In these fields, we detect HII regions and diffuse ionized gas to unprecedented depth. About 15% of the ionized gas was undetected by previous observing campaigns. This newly detected faint ionized gas is visible everywhere around the central merger, and shows filamentary structure. We estimate diffuse gas fractions of about 60% in the central field and 10% in the southern region. We are able to show that the southern region contains a significantly different population of HII regions, showing fainter luminosities. By comparing HII region luminosities with the HST catalog of young star clusters in the central field, we estimate that there is enough Lyman-continuum leakage in the merger to explain the amount of diffuse ionized gas that we detect. We compare the Lyman-continuum escape fraction of each HII region against ionization-parameter sensitive emission line ratios. While we find no systematic trend between these properties, the most extreme line ratios seem to be strong indicators of density bounded ionization. Extrapolating the Lyman-continuum escape fractions to the southern region, we conclude that just from the comparison of the young stellar populations to the ionized gas there is no need to invoke other ionization mechanisms than Lyman-continuum leaking HII regions for the diffuse ionized gas in the Antennae.

[67] arXiv:1712.04451v1 [pdf, vox]

Slicing COSMOS with SC4K: the evolution of typical Lya emitters and the Lya escape fraction from z~2 to z~6

David Sobral, Sérgio Santos, Jorryt Matthee, Ana Paulino-Afonso, Bruno Ribeiro, João Calhau, Ali A. Khostovan
Submitted Tuesday 12 December 2017 @ 19:00:01 GMT
Submitted to MNRAS. 23 pages + Appendices with SC4K catalogue and LFs. SC4K catalogue of LAEs, SC4K LFs and the S-SC4K compilation are available (https://goo.gl/q9yf​Ko) prior to publication

We present and explore deep narrow- and medium-band data obtained with the Subaru and the Isaac Newton telescopes in the ~2 deg$^2$ COSMOS field. We use these data as an extremely wide, low-resolution (R~20-80) IFU survey to slice through the COSMOS field and obtain a large sample of ~4000 Lyman-$\alpha$ (Lya) emitters from z~2 to z~6 in 16 redshift slices (SC4K). We present new Lya luminosity functions (LFs) covering a co-moving volume of ~10$^8$Mpc$^3$. SC4K extensively complements ultra-deep surveys, jointly covering over 4 dex in Lya luminosity and revealing a global (2.5<z<6) synergy LF with $\alpha=-1.93\pm0.12​$, $\log_{10}\Phi^*=-3.​45^{+0.22}_{-0.29}$ Mpc$^{-3}$ and $\log_{10}L^*=42.93^​{+0.15}_{-0.11}$ erg/s. The Schechter component of the Lya LF reveals a factor ~5 rise in $L^*$ and a ~7x decline in $\Phi^*$ from z~2 to z~6. The data reveal an extra power-law (or Schechter) component above L~10$^{43.3}$ erg/s at z~2.2-3.5 and we show that it is partially driven by X-ray and radio AGN, as their Lya LF resembles the excess. The power-law component vanishes and/or is below our detection limits above z>3.5, likely linked with the evolution of the AGN population. The Lya luminosity density rises by a factor ~2 from z~2 to z~3 but is then found to be roughly constant (~$1.1\times10^{40}$ erg s$^{-1}$ Mpc$^{-3}$) to z~6, despite the ~0.7 dex drop in UV luminosity density. The Lya/UV luminosity density ratio rises from $4\pm1$% to $30\pm6$% from z~2.2 to z~6. Our results imply a rise of a factor of ~2 in the global ionisation efficiency ($\xi_{\rm ion}$) and a factor ~$4\pm1$ in the Lya escape fraction from z~2 to z~6, hinting for evolution in both the typical burstiness/stellar populations and even more so in the typical ISM conditions allowing Ly$\alpha$ photons to escape.

[68] arXiv:1712.04452v1 [pdf, vox]

Inferring the star-formation histories of massive quiescent galaxies with BAGPIPES: Evidence for multiple quenching mechanisms

A. C. Carnall, R. J. McLure, J. S. Dunlop, R. Davé
Submitted Tuesday 12 December 2017 @ 19:00:01 GMT
24 pages, 16 figures, submitted to MNRAS

We present Bayesian Analysis of Galaxies for Physical Inference and Parameter EStimation, or BAGPIPES, a new Python tool which can be used to rapidly generate complex model galaxy spectra and to fit these to arbitrary combinations of spectroscopic and photometric data using the MultiNest algorithm. We extensively test our ability to recover realistic star-formation histories (SFHs) with BAGPIPES by fitting mock observations of quiescent galaxies from the MUFASA simulation. We show that a double-power-law model produces better agreement with realistic SFHs than an exponentially-declin​ing model. We then perform a detailed analysis of the SFHs of a sample of 9312 quiescent galaxies from UltraVISTA with stellar masses, $M_* > 10^{10}\ \mathrm{M_\odot}$ and redshifts $0.25 < z_\mathrm{obs} < 3.75$. The majority of our quiescent sample exhibit SFHs which rise gradually then quench relatively rapidly, over $\sim 1{-}2$ Gyr. This behaviour is consistent with recent cosmological hydrodynamic simulations, where AGN-driven feedback in the low-accretion (jet) mode is the dominant quenching mechanism. In addition, we identify two further subsets of objects with distinct SFH shapes. At $z_\mathrm{obs} \gtrsim 1$ we find a class of objects with SFHs which rise and fall very rapidly, with quenching timescales of $\lesssim 1$ Gyr. These objects are consistent with (potentially merger-triggered) quasar-mode AGN feedback. Also, at $z_\mathrm{obs} \lesssim 1$ we find a population with SFHs which quench more slowly than they rise, over $\gtrsim3$ Gyr, which we speculate to be the result of a 'natural' quenching process, where galaxy SFHs die down gradually due to the diminishing overall cosmic gas supply. Purely passive evolution of the quiescent population at $z_\mathrm{obs} \gtrsim 0.5$ is disfavoured by our results.

[69] arXiv:1712.04448v1 [pdf, vox]

On the radial acceleration relation of $Λ$CDM satellite galaxies

Enrico Garaldi, Emilio Romano-Díaz, Cristiano Porciani, Marcel S. Pawlowski
Submitted Tuesday 12 December 2017 @ 19:00:00 GMT
5 pages, 4 figures, comments welcome

The radial acceleration measured in bright galaxies tightly correlates with that generated by the observed distribution of baryons, a phenomenon known as the radial acceleration relation (RAR). Dwarf spheroidal satellite galaxies have been recently found to depart from the extrapolation of the RAR measured for more massive objects but with a substantially larger scatter. If confirmed by new data, this result provides a powerful test of the theory of gravity at low accelerations that requires robust theoretical predictions. By using high-resolution hydrodynamical simulations, we show that, within the standard model of cosmology ($\Lambda$CDM), satellite galaxies are expected to follow the same RAR as brighter systems but with a much larger scatter which does not correlate with the physical properties of the galaxies. In the simulations, the RAR evolves mildly with redshift. Moreover, the acceleration due to the gravitational field of the host has no effect on the RAR. This is in contrast with the External Field Effect in Modified Newtonian Dynamics (MOND) which causes galaxies in strong external fields to have lower internal accelerations. This difference between $\Lambda$CDM and MOND offers a possible way to discriminate between them.

[70] arXiv:1712.04437v1 [pdf, vox]

Can Advanced LIGO detect gravitons of energy $\hbarω$ as excess shot noise at 1 kHz?

Richard Lieu
Submitted Tuesday 12 December 2017 @ 18:50:12 GMT
4 pages

The discovery of GW170104 by the Advanced LIGO and Virgo Collaboration revealed not only that gravitational waves propagate at the speed of light to a high degree of accuracy (5 parts in 10$^{16}$), but also this speed is independent of frequency, \ie~if gravitons exist they are massless just like photons. If, as in the case of light, gravitational waves are quantized into gravitons $\hbar\om$ where $\om$ is the angular frequency of the wave, it will be possible to estimate the number of gravitons $N$ associated with a LIGO signal of duration $T$, by calculating the total energy of the signal from the motion of the mirrors. For the representative values of $T = 1$~s and $\om = 63$~Hz, we find $N \ap 2.54 \times 10^8$, corresponds to a spectral strain of $\tilde h \ap 3 \times 10^{-23}$~Hz$^{-1/2}​$ at all frequencies and wave amplitudes, due to graviton shot noise. This strain is 100 times below the sensitivity of Advanced LIGO. More generally, however, for waves of any frequency the sensitivity threshold at sampling frequency 1~kHz is given by the inequality $M\om^2 < 400$g~Hz$^2$ (where $M$ is the mass of the mirror) and favors waves of lower frequencies irrespective of their amplitude, provided the observing time is long enough for some gravitons to be collected. Thus it could well be that Advanced LIGO already detected the graviton as an excess shot noise component not yet accounted for.

[71] arXiv:1712.04435v1 [pdf, vox]

Ejection of rocky and icy material from binary star systems: Implications for the origin and composition of 1I/`Oumuamua

Alan P. Jackson, Daniel Tamayo, Noah Hammond, Mohamad Ali-Dib, Hanno Rein
Submitted Tuesday 12 December 2017 @ 18:47:47 GMT
5 pages, 2 figures. Submitted to MNRAS letters

In single star systems like our own Solar system, comets dominate the mass budget of bodies that are ejected into interstellar space, since they form further away and are less tightly bound. However 1I/`Oumuamua, the first interstellar object detected, appears asteroidal in its spectra and in its lack of detectable activity. We argue that the galactic budget of interstellar objects like 1I/`Oumuamua should be dominated by planetesimal material ejected during planet formation in circumbinary systems, rather than in single star systems or widely separated binaries. We further show that in circumbinary systems, rocky bodies should be ejected in comparable numbers to icy ones. This suggests that a substantial fraction of additional interstellar objects discovered in the future should display an active coma. We find that the rocky population, of which 1I/`Oumuamua seems to be a member, should be predominantly sourced from A-type and late B-star binaries.

[72] arXiv:1712.04423v1 [pdf, vox]

Distances to Supernova Remnants G$20.4+0.1$, G$24.7-0.6$, G$28.6-0.1$ and G$42.0-0.1$ and New Molecular Cloud Associations

S. Ranasinghe, D. A. Leahy
Submitted Tuesday 12 December 2017 @ 18:28:25 GMT
14 pages, 16 figures

Accurate distances to supernova remnants (SNRs) are crucial in determining their size, age, luminosity and evolutionary state. To determine distances, we chose four SNRs from the VLA Galactic Plane Survey (VGPS) for extraction of HI absorption spectra. Analysing HI absorption spectra, $^{13}$CO emission spectra, and HI and $^{13}$CO channel maps, kinematic velocities (or their limits) to the four SNRs were calculated. The four SNRs are probably associated with molecular clouds and the new distance to G$20.4+0.1$, G$24.7-0.6$, G$28.6-0.1$ and G$42.0-0.1$ are $7.8 \pm0.2$ kpc, $3.8\pm 0.2 $ kpc, $ 9.6 \pm 0.3 $ kpc and $ 3.5 \pm 0.4 $ kpc, respectively.

[73] arXiv:1712.04409v1 [pdf, vox]

Explaining the elongated shape of 'Oumuamua by the Eikonal abrasion model

Gábor Domokos, András A. Sipos, Gyula M. Szabó, Péter L. Várkonyi
Submitted Tuesday 12 December 2017 @ 17:59:36 GMT
Accepted by the Research Notes of the AAS

The photometry of the minor body with extrasolar origin (1I/2017 U1) 'Oumuamua revealed an unprecedented shape: Meech et al. (2017) reported a shape elongation b/a close to 1/10, which calls for theoretical explanation. Here we show that the abrasion of a primordial asteroid by a huge number of tiny particles ultimately leads to such elongated shape. The model (called the Eikonal equation) predicting this outcome was already suggested in Domokos et al. (2009) to play an important role in the evolution of asteroid shapes.

[74] arXiv:1712.04403v1 [pdf, vox]

A Hubble Space Telescope Imaging Study of Four FeLoBAL Quasar Host Galaxies

Daniel Lawther, Marianne Vestergaard, Xiaohui Fan
Submitted Tuesday 12 December 2017 @ 17:40:19 GMT
33 pages, 15 figures. Accepted for publication in MNRAS

We study the host galaxies of four Iron Low-Ionization Broad Absorption-line Quasars (FeLoBALs) using Hubble Space Telescope imaging data, investigating the possibility that they represent a transition between an obscured AGN and an ordinary optical quasar. In this scenario, the FeLoBALs represent the early stage of merger-triggered accretion, in which case their host galaxies are expected to show signs of an ongoing or recent merger. Using PSF subtraction techniques, we decompose the images into host galaxy and AGN components at rest-frame ultraviolet and optical wavelengths. The ultraviolet is sensitive to young stars, while the optical probes stellar mass. In the ultraviolet we image at the BAL absorption trough wavelengths so as to decrease the contrast between the quasar and host galaxy emission. We securely detect an extended source for two of the four FeLoBALs in the rest-frame optical; a third host galaxy is marginally detected. In the rest-frame UV we detect no host emission; this constrains the level of unobscured star formation. Thus, the host galaxies have observed properties that are consistent with those of non-BAL quasars with the same nuclear luminosity, i.e., quiescent or moderately starforming elliptical galaxies. However, we cannot exclude starbursting hosts that have the stellar UV emission obscured by modest amounts of dust reddening. Thus, our findings also allow the merger-induced young quasar scenario. For three objects, we identify possible close companion galaxies that may be gravitationally interacting with the quasar hosts.

[75] arXiv:1712.04398v1 [pdf, vox]

Stability of a black hole and the speed of gravity waves within self-tuning cosmological models

Eugeny Babichev, Christos Charmousis, Gilles Esposito-Farese, Antoine Lehébel
Submitted Tuesday 12 December 2017 @ 17:19:08 GMT
5 pages, no figure, RevTeX4 format

The gravitational wave event GW170817 together with its electromagnetic counterparts constrains the speed of gravity to be extremely close to that of light. We first show, on the example of an exact Schwarzschild-de Sitter solution of a specific beyond-Horndeski theory, that imposing the strict equality of these speeds in the asymptotic homogeneous Universe suffices to guarantee so even in the vicinity of the black hole, where large curvature and scalar-field gradients are present. We also find that the solution is stable in a range of the model parameters. We finally show that an infinite class of beyond-Horndeski models satisfying the equality of gravity and light speeds still provide an elegant self-tuning: The very large bare cosmological constant entering the Lagrangian is almost perfectly counterbalanced by the energy-momentum tensor of the scalar field, yielding a tiny observable effective cosmological constant.

[76] arXiv:1712.04394v1 [pdf, vox]

Molecules in the early Universe

B. Novosyadlyj, O. Sergijenko, V. M. Shulga
Submitted Tuesday 12 December 2017 @ 17:05:16 GMT
12 pages, 1 figure, 3 tables

We study the formation of first molecules, negative Hydrogen ions and molecular ions in model of the Universe with cosmological constant and cold dark matter. The cosmological recombination is described in the framework of modified model of the effective 3-level atom, while the kinetics of chemical reactions in the framework of the minimal model for Hydrogen, Deuterium and Helium. It is found that the uncertainties of molecular abundances caused by the inaccuracies of computation of cosmological recombination are about 2-3%. The uncertainties of values of cosmological parameters affect the abundances of molecules, negative Hydrogen ions and molecular ions at the level of up to 2%. In the absence of cosmological reionization at redshift $z=10$ the ratios of abundances to the Hydrogen one are $3.08\times10^{-13}$ for $H^-$, $2.37\times10^{-6}$ for $H_2$, $1.26\times10^{-13}$ for $H_2^+$, $1.12\times10^{-9}$ for $HD$ and $8.54\times10^{-14}$ for $HeH^+$.

[77] arXiv:1712.04390v1 [pdf, vox]

More Rapidly Rotating PMS M Dwarfs with Light Curves Suggestive of Orbiting Clouds of Material

John Stauffer, Luisa Rebull, Trevor David, Moira Jardine, Andrew Collier Cameron, Ann Marie Cody, Lynne Hillenbrand, David Barrado, Julian van Eyken, Carl Melis, Cesar Briceno
Submitted Tuesday 12 December 2017 @ 16:59:04 GMT
Accepted by AJ; 22 pages, 15 figures

In a previous paper, using data from K2 Campaign 2, we identified 11 very low mass members of the $\rho$ Oph and Upper Scorpius star-forming region as having periodic photometric variability and phased light curves showing multiple scallops or undulations. All the stars with the "scallop-shell" light curve morphology are mid-to-late M dwarfs without evidence of active accretion, and with photometric periods generally $<$1 day. Their phased light curves have too much structure to be attributed to non-axisymmetrically distributed photospheric spots and rotational modulation. We have now identified an additional eight probable members of the same star-forming region plus three stars in the Taurus star-forming region with this same light curve morphology and sharing the same period and spectral type range as the previous group. We describe the light curves of these new stars in detail and present their general physical characteristics. We also examine the properties of the overall set of stars in order to identify common features that might help elucidate the causes of their photometric variability.

[78] arXiv:1712.04380v1 [pdf, vox]

Cosmographic analysis with Chebyshev polynomials

Salvatore Capozziello, Rocco D'Agostino, Orlando Luongo
Submitted Tuesday 12 December 2017 @ 16:36:38 GMT
17 pages, 6 figures, 5 tables

The limits of standard cosmography are here revised addressing the problem of error propagation during statistical analyses. To do so, we propose the use of Chebyshev polynomials to parameterize cosmic distances. In particular, we demonstrate that building up rational Chebyshev polynomials significantly reduces error propagations with respect to standard Taylor series. This technique provides unbiased estimations of the cosmographic parameters and performs significatively better than previous numerical approximations. To figure this out, we compare rational Chebyshev polynomials with Pad\'e series. In addition, we theoretically evaluate the convergence radius of (1,1) Chebyshev rational polynomial and we compare it with the convergence radii of Taylor and Pad\'e approximations. We thus focus on regions in which convergence of Chebyshev rational functions is better than standard approaches. With this recipe, as high-redshift data are employed, rational Chebyshev polynomials remain highly stable and enable one to derive highly accurate analytical approximations of Hubble's rate in terms of the cosmographic series. Finally, we check our theoretical predictions by setting bounds on cosmographic parameters through Monte Carlo integration techniques, based on the Metropolis-Hastings algorithm. We apply our technique to high-redshift cosmic data, using the JLA supernovae sample and the most recent versions of Hubble parameter and baryon acoustic oscillation measurements. We find that cosmography with Taylor series fails to be predictive with the aforementioned data sets, while turns out to be much more stable using the Chebyshev approach.

[79] arXiv:1712.04378v1 [pdf, vox]

PArthENoPE reloaded

R. Consiglio, P. F. de Salas, G. Mangano, G. Miele, S. Pastor, O. Pisanti
Submitted Tuesday 12 December 2017 @ 16:31:00 GMT
13 pages, 5 figures

We describe the main features of a new and updated version of the program PArthENoPE, which computes the abundances of light elements produced during Big Bang Nucleosynthesis. As the previous first release in 2008, the new one, PArthENoPE 2.0, will be soon publicly available and distributed from the code site, http://parthenope.na​.infn.it. Apart from minor changes, which will be also detailed, the main improvements are as follows. The powerful, but not freely accessible, NAG routines have been substituted by ODEPACK libraries, without any significant loss in precision. Moreover, we have developed a Graphical User Interface (GUI) which allows a friendly use of the code and a simpler implementation of running for grids of input parameters. Finally, we report the results of PArthENoPE 2.0 for a minimal BBN scenario with free radiation energy density.

[80] arXiv:1712.04373v1 [pdf, vox]

Constraining the properties of the magnetic turbulence in the Geminga region using HAWC $γ$-ray data

Rubén López-Coto, Gwenael Giacinti
Submitted Tuesday 12 December 2017 @ 16:16:12 GMT
submitted to MNRAS

Observations of extended gamma-ray emission around Galactic cosmic-ray (CR) sources can be used as novel probes of interstellar magnetic fields. Using very-high-energy gamma-ray data from the HAWC Observatory, we place constraints on the properties of the magnetic turbulence within $\approx 25$ pc from Geminga. We inject and propagate individual CR electrons in 3D realizations of turbulent magnetic fields, calculate the resulting gamma-ray emission, and compare with HAWC measurements of this region. We find that HAWC data is compatible with expectations for Kolmogorov or Kraichnan turbulence, and can be well fitted for reasonable coherence lengths and strengths of the turbulence, despite implying a CR diffusion coefficient significantly smaller than those suggested by Galactic CR propagation codes. The best fit is found for a coherence length $L_{\rm c} \approx 1$ pc and a magnetic field strength $B_{\rm rms} \approx 3 \mu$G, and the preferred value for $L_{\rm c}$ increases with $B_{\rm rms}$. Moreover, the apparent lack of strong asymmetries in the observed emission allows us to constrain the coherence length to $L_{\rm c} \lesssim 5$ pc in this region.

[81] arXiv:1712.04360v1 [pdf, vox]

A direct measurement of sense of rotation of PSR J0737$-$3039A

Nihan Pol, Maura McLaughlin, Michael Kramer, Ingrid Stairs, Benetge B. P. Perera, Andrea Possenti
Submitted Tuesday 12 December 2017 @ 15:52:39 GMT
Accepted for publication in ApJ

We apply the algorithm published by Liang et al. (2014) to describe the Double Pulsar system J0737$-$3039 and extract the sense of rotation of first born recycled pulsar PSR J0737$-$3039A. We find that this pulsar is rotating prograde in its orbit. This is the first direct measurement of the sense of rotation of a pulsar with respect to its orbit and a direct confirmation of the rotating lighthouse model for pulsars. This result confirms that the spin angular momentum vector is closely aligned with the orbital angular momentum, suggesting that kick of the supernova producing the second born pulsar J0737$-$3039B was small.

[82] arXiv:1712.04446v1 [pdf, vox]

Nitrogen oxide in protostellar envelopes and shocks: the ASAI survey

C. Codella, S. Viti, B. Lefloch, J. Holdship, R. Bachiller, E. Bianchi, C. Ceccarelli, C. Favre, I. Jiménez-Serra, L. Podio, M. Tafalla
Submitted Tuesday 12 December 2017 @ 15:50:38 GMT
MNRAS, in press

The high-sensitivity of the IRAM 30-m ASAI unbiased spectral survey in the mm-window allows us to detect NO emission towards both the Class I object SVS13-A and the protostellar outflow shock L1157-B1. We detect the hyperfine components of the $^2\Pi_{\rm 1/2}$ $J$ = 3/2 $\to$ 1/2 (at 151 GHz) and the $^2\Pi_{\rm 1/2}$ $J$ = 5/2 $\to$ 3/2 (250 GHz) spectral pattern. The two objects show different NO profiles: (i) SVS13-A emits through narrow (1.5 km s$^{-1}$) lines at the systemic velocity, while (ii) L1157-B1 shows broad ($\sim$ 5 km s$^{-1}$) blue-shifted emission. For SVS13-A the analysis leads to $T_{\rm ex}$ $\geq$ 4 K, $N(\rm NO)$ $\leq$ 3 $\times$ 10$^{15}$ cm$^{-2}$, and indicates the association of NO with the protostellar envelope. In L1157-B1, NO is tracing the extended outflow cavity: $T_{\rm ex}$ $\simeq$ 4--5 K, and $N(\rm NO)$ = 5.5$\pm$1.5 $\times$ 10$^{15}$ cm$^{-2}$. Using C$^{18}$O, $^{13}$C$^{18}$O, C$^{17}$O, and $^{13}$C$^{17}$O ASAI observations we derive an NO fractional abundance less than $\sim$ 10$^{-7}$ for the SVS13-A envelope, in agreement with previous measurements towards extended PDRs and prestellar objects. Conversely, a definite $X(NO)$ enhancement is measured towards L1157-B1, $\sim$ 6 $\times$ 10$^{-6}$, showing that the NO production increases in shocks. The public code UCLCHEM was used to interpret the NO observations, confirming that the abundance observed in SVS13-A can be attained in an envelope with a gas density of 10$^5$ cm$^{-3}$ and a kinetic temperature of 40 K. The NO abundance in L1157-B1 is reproduced with pre-shock densities of 10$^5$ cm$^{-3}$ subjected to a $\sim$ 45 km s$^{-1}$ shock.

[83] arXiv:1712.04324v1 [pdf, vox]

HATS-50b through HATS-53b: four transiting hot Jupiters orbiting G-type stars discovered by the HATSouth survey

Th. Henning, L. Mancini, P. Sarkis, G. A. Bakos, J. D. Hartman, D. Bayliss, J. Bento, W. Bhatti, R. Brahm, S. Ciceri, Z. Csubry, M. de Val-Borro, N. Espinoza, B. J. Fulton, A. W. Howard, H. T. Isaacson, A. Jordan, G. W. Marcy, K. Penev, M. Rabus, V. Suc, T. G. Tan, C. G. Tinney, D. J. Wright, G. Zhou, S. Durkan, J. Lazar, I. Papp, P. Sari
Submitted Tuesday 12 December 2017 @ 14:52:55 GMT
28, pages, 14 figures, accepted for publication in The Astronomical Journal

We report the discovery of four close-in transiting exoplanets, HATS-50 through HATS-53, discovered using the HATSouth three-continent network of homogeneous and automated telescopes. These new exoplanets belong to the class of hot Jupiters and orbit G-type dwarf stars, with brightness in the range V=12.5-14.0 mag. While HATS-53 has many physical characteristics similar to the Sun, the other three stars appear to be metal rich, larger and more massive. Three of the new exoplanets, namely HATS-50, HATS-51 and HATS-53, have low density and similar orbital period. Instead, HATS-52 is more dense and has a shorter orbital period. It also receives an intensive radiation from its parent star and, consequently, presents a high equilibrium temperature. HATS-50 shows a marginal additional transit feature consistent with an ultra-short period hot super Neptune, which will be able to be confirmed with TESS photometry.

[84] arXiv:1712.04317v1 [pdf, vox]

Cosmic acceleration from a single fluid description

Salvatore Capozziello, Rocco D'Agostino, Orlando Luongo
Submitted Tuesday 12 December 2017 @ 14:45:20 GMT
13 pages, 7 figures

We here propose a new class of barotropic factor for matter, motivated by properties of isotropic deformations of crystalline solids. Our approach is dubbed Anton-Schmidt's equation of state and provides a non-vanishing, albeit small, pressure term for matter. The corresponding pressure is thus proportional to the logarithm of universe's volume, i.e. to the density itself since $V\propto \rho^{-1}$. In the context of solid state physics, we demonstrate that by only invoking standard matter with such a property, we are able to frame the universe speed up in a suitable way, without invoking a dark energy term by hand. Our model extends a recent class of dark energy paradigms named \emph{logotropic} dark fluids and depends upon two free parameters, namely $n$ and $B$. Within the Debye approximation, we find that $n$ and $B$ are related to the Gr\"uneisen parameter and the bulk modulus of crystals. We thus show the main differences between our model and the logotropic scenario, and we highlight the most relevant properties of our new equation of state on the background cosmology. Discussions on both kinematics and dynamics of our new model have been presented. We demonstrate that the $\Lambda$CDM model is inside our approach, as limiting case. Comparisons with CPL parametrization have been also reported in the text. Finally, a Monte Carlo analysis on the most recent low-redshift cosmological data allowed us to place constraints on $n$ and $B$. In particular, we found $n=-0.147^{+0.113}_{​-0.107}$ and $B=3.54 \times 10^{-3}$.

[85] arXiv:1712.04316v1 [pdf, vox]

On the radio and GeV-TeV gamma-ray emission connection in Fermi blazars

R. Lico, M. Giroletti, M. Orienti, L. Costamante, V. Pavlidou, F. D'Ammando, F. Tavecchio
Submitted Tuesday 12 December 2017 @ 14:42:45 GMT
6 pages, 2 figures, 1 table. For the proceedings of the 7th International Fermi Symposium

The Fermi-LAT revealed that the census of the gamma-ray sky is dominated by blazars. Looking for a possible connection between radio and gamma-ray emission is a central issue for understanding the blazar physics, and various works were dedicated to this topic. However, while a strong and significant correlation was found between radio and gamma-ray emission in the 0.1-100 GeV energy range, the connection between radio and very high energy (VHE, E>0.1 TeV) emission is still elusive. The main reason is the lack of a homogeneous VHE sky coverage, due to the operational mode of the imaging atmospheric Cherenkov telescopes. With the present work we aim to quantify and assess the significance of the possible connection between high-resolution radio emission, on milliarcsecond scale, and GeV-TeV gamma-ray emission in blazars. For achieving our goal we extract two large and unbiased blazar samples from the 1FHL and 2FHL Fermi catalogs, above 10 GeV and 50 GeV, respectively. To investigate how the correlation evolves as the gamma-ray energy increases, we perform the same analysis by using the 0.1-300 GeV 3FGL gamma-ray energy fluxes. When we consider the 0.1-300 GeV gamma-ray energy range, we find a strong and significant correlation for all of the blazar sub-classes. Conversely, when we consider the gamma-ray emission above 10 GeV the correlation with the radio emission vanishes, with the exception of the blazar sub-class of high synchrotron peaked objects.

[86] arXiv:1712.04289v1 [pdf, vox]

Model-Independent Predictions for Smooth Cosmic Acceleration Scenarios

Vinicius Miranda, Cora Dvorkin
Submitted Tuesday 12 December 2017 @ 13:51:09 GMT
18 pages, 16 figures

Through likelihood analyses of both current and future data that constrain both the expansion history of the universe and the clustering of matter fluctuations, we provide falsifiable predictions for three broad classes of models that explain the accelerated expansions of the universe: $\Lambda$CDM, the quintessence scenario and a more general class of smooth dark energy models that can cross the phantom barrier $w(z)=-1$. Our predictions are model independent in the sense that we do not rely on a specific parametrization, but we instead use a principal component (PC) basis function constructed a priori from a noise model of supernovae and Cosmic Microwave Background observations. For the supernovae measurements, we consider two type of surveys: the current JLA and the upcoming WFIRST surveys. We show that WFIRST will be able to improve growth predictions in curved models significantly. The remaining degeneracy between spatial curvature and $w(z)$ could be overcome with improved measurements of $\sigma_8 \Omega_m^{1/2}$, a combination that controls the amplitude of the growth of structure. We also point out that a PC-based Figure of Merit reveals that the usual two-parameter description of $w(z)$ does not exhaust the information that can be extracted from current data (JLA) or future data (WFIRST).

[87] arXiv:1712.04284v1 [pdf, vox]

Photometric observations of nine Transneptunian objects and Centaurs

T. Hromakina, D. Perna, I. Belskaya, E. Dotto, A. Rossi, F. Bisi
Submitted Tuesday 12 December 2017 @ 13:34:35 GMT

We present the results of photometric observations of six Transneptunian objects and three Centaurs, estimations of their rotational periods and corresponding amplitudes. For six of them we present also lower limits of density values. All observations were made using 3.6-m TNG telescope (La Palma, Spain). For four objects -- (148975) 2001 XA255, (281371) 2008 FC76, (315898) 2008 QD4, and 2008 CT190 -- the estimation of short-term variability was made for the first time. We confirm rotation period values for two objects: (55636) 2002 TX300 and (202421) 2005 UQ513, and improve the precision of previously reported rotational period values for other three -- (120178) 2003 OP32, (145452) 2005 RN43, (444030) 2004 NT33 -- by using both our and literature data. We also discuss here that small distant bodies, similarly to asteroids in the Main belt, tend to have double-peaked rotational periods caused by the elongated shape rather than surface albedo variations.

[88] arXiv:1712.04280v1 [pdf, vox]

HD 156324: a tidally locked magnetic triple spectroscopic binary with a disrupted magnetosphere

M. Shultz, Th. Rivinius, G. A. Wade, E. Alecian, V. Petit, the BinaMIcS Collaboration
Submitted Tuesday 12 December 2017 @ 13:23:31 GMT
15 pages, 10 figures, 3 tables, accepted for publication in MNRAS (reference MN-17-3873-MJ.R1)

HD 156324 is an SB3 (B2V/B5V/B5V) system in the Sco OB4 association. The He-strong primary possesses both a strong magnetic field, and H$\alpha$ emission believed to originate in its Centrifugal Magnetosphere (CM). We analyse a large spectroscopic and high-resolution spectropolarimetric dataset. The radial velocities (RVs) indicate that the system is composed of two sub-systems, which we designate A and B. Period analysis of the RVs of the three components yields orbital periods $P_{\rm orb} = 1.5806(1)$~d for the Aa and Ab components, and 6.67(2)~d for the B component, a PGa star. Period analysis of the longitudinal magnetic field \bz~and H$\alpha$ equivalent widths, which should both be sensitive to the rotational period $P_{\rm rot}$ of the magnetic Aa component, both yield $\sim$1.58~d. Since $P_{\rm orb} = P_{\rm rot}$ Aa and Ab must be tidally locked. Consistent with this, the orbit is circularized, and the rotational and orbital inclinations are identical within uncertainty, as are the semi-major axis and the Kepler corotation radius. The star's H$\alpha$ emission morphology differs markedly from both theoretical and observational expectations in that there is only one, rather than two, emission peaks. We propose that this unusual morphology may be a consequence of modification of the gravitocentrifugal potential by the presence of the close stellar companion. We also obtain upper limits on the magnetic dipole strength $B_{\rm d}$ for the Ab and B components, respectively finding $B_{\rm d} < 2.6$~kG and $<0.7$~kG.

[89] arXiv:1712.04445v1 [pdf, vox]

PSR J2322$-$2650 -- A low-luminosity millisecond pulsar with a planetary-mass companion

R. Spiewak, M. Bailes, E. D. Barr, N. D. R. Bhat, M. Burgay, A. D. Cameron, D. J. Champion, C. M. L. Flynn, A. Jameson, S. Johnston, M. J. Keith, M. Kramer, S. R. Kulkarni, L. Levin, A. G. Lyne, V. Morello, C. Ng, A. Possenti, V. Ravi, B. W. Stappers, W. van Straten, C. Tiburzi
Submitted Tuesday 12 December 2017 @ 13:01:10 GMT
10 pages, 6 figures; accepted for publication in MNRAS

We present the discovery of a binary millisecond pulsar (MSP), PSR J2322$-$2650, found in the Southern section of the High Time Resolution Universe survey. This system contains a 3.5-ms pulsar with a $\sim10^{-3}$ M$_{\odot}$ companion in a 7.75-hour circular orbit. Follow-up observations at the Parkes and Lovell telescopes have led to precise measurements of the astrometric and spin parameters, including the period derivative, timing parallax, and proper motion. PSR J2322$-$2650 has a parallax of $4.4\pm1.2$ mas, and is thus at an inferred distance of $230^{+90}_{-50}$ pc, making this system a candidate for optical studies. We have detected a source of $R\approx26.4$ mag at the radio position in a single $R$-band observation with the Keck Telescope, and this is consistent with the blackbody temperature we would expect from the companion if it fills its Roche lobe. The intrinsic period derivative of PSR J2322$-$2650 is among the lowest known, $4.4(4)\times10^{-22​}$ s s$^{-1}$, implying a low surface magnetic field strength, $4.0(4)\times10^7$ G. Its mean radio flux density of 160 $\mu$Jy combined with the distance implies that its radio luminosity is the lowest ever measured, $0.008(5)$ mJy kpc$^2$. The inferred population of these systems in the Galaxy may be very significant, suggesting that this is a common MSP evolutionary path.

[90] arXiv:1712.04271v1 [pdf, vox]

Discovery of GeV gamma-ray emission from the LMC B0443-6657 with the Fermi Large Area Telescope

Qing-Wen Tang
Submitted Tuesday 12 December 2017 @ 12:57:09 GMT
11 pages, 5 figures, submitted for publication in Ap&SS

We report the discovery of gamma-ray detection from the LMC B0443-6657 using the Large Area Telescope (LAT) on board the [Fermi Gamma-ray Space Telescope]. LMC B0443-6657 is a flat spectrum radio source. Employing the 8 years of the LAT observations between 0.2-100~GeV, our result reveals a significant excess ($>9.4\sigma$) above the background, which is based on either the 4-years LAT catalog or the best source model of 73.3 months data. A power law model is assessed to be adequate to describe the $0.2-100$ GeV $\gamma$-ray spectrum and yields a flux of $3.27\pm0.53\ \mathrm{photon\ \,cm}^2\ \mathrm{s}^{-1}$ with photon index $2.35\pm0.11$, corresponding to an isotropic gamma-ray luminosity of $5.3\times10^{40}\ \mathrm{erg\ \,s}^{-1}$. The hadronic model predicts a low X-ray or TeV flux while the leptonic predicts an observable flux in these two energy bands. The follow-up observations of the LMC B0443-6657 in X-ray or TeV band would help constrain the contribution from the CR electrons and protons.

[91] arXiv:1712.04267v1 [pdf, vox]

Gravitational-wave luminosity of binary neutron stars mergers

Francesco Zappa, Sebastiano Bernuzzi, David Radice, Albino Perego, Tim Dietrich
Submitted Tuesday 12 December 2017 @ 12:41:25 GMT
5 pages, 4 figures

We study the gravitational-wave peak luminosity and radiated energy of quasicircular neutron star mergers using a large sample of numerical relativity simulations with different binary parameters and input physics. The peak luminosity for all the binaries can be described in terms of the mass ratio and of the leading-order post-Newtonian tidal parameter solely. The mergers resulting in a prompt collapse to black hole have largest peak luminosities. However, the largest amount of energy per unit mass is radiated by mergers that produce a hypermassive neutron star or a massive neutron star remnant. We quantify the gravitational-wave luminosity of binary neutron star merger events, and set upper limits on the radiated energy and the remnant angular momentum from these events. We find that there is an empirical universal relation connecting the total gravitational radiation and the angular momentum of the remnant. Our results constrain the final spin of the remnant black-hole and also indicate that stable neutron star remnant forms with super-Keplerian angular momentum.

[92] arXiv:1712.04237v1 [pdf, vox]

Hybrid Higgs Inflation: The Use of Disformal Transformation

Seiga Sato, Kei-ichi Maeda
Submitted Tuesday 12 December 2017 @ 11:15:36 GMT
16 pages, 6 figures, 1 table

We propose a hybrid type of the conventional Higgs inflation and new Higgs inflation models. We perform a disformal transformation into the Einstein frame and analyze the background dynamics and the cosmological perturbations in the truncated model, in which we ignore the higher-derivative terms of the Higgs field. From the observed power spectrum of the density perturbations, we obtain the constraint on the non-minimal coupling constant $\xi$ and the mass parameter $M$ in the derivative coupling. Although the primordial tilt $n_s$ in the hybrid model barely changes, the tensor-to-scalar ratio $r$ moves from the value in new Higgs inflationary model to that in the conventional Higgs inflationary model as $|\xi|$ increases. We confirm our results by numerical analysis by ADM formalism of the full theory in the Jordan frame.

[93] arXiv:1712.04232v1 [pdf, vox]

An X-ray survey of the central molecular zone: variability of the Fe Ka emission line

R. Terrier, M. Clavel, S. Soldi, A. Goldwurm, G. Ponti, M. R. Morris, D. Chuard
Submitted Tuesday 12 December 2017 @ 11:07:13 GMT
Accepted for publication in A&A

There is now abundant evidence that the luminosity of the Galactic super-massive black hole (SMBH) has not always been as low as it is nowadays. The observation of varying non-thermal diffuse X-ray emission in molecular complexes in the central 300 pc has been interpreted as delayed reflection of a past illumination by bright outbursts of the SMBH. The observation of different variability timescales of the reflected emission in the Sgr A molecular complex can be well explained if the X-ray emission of at least two distinct and relatively short events (i.e. about 10 years or less) is currently propagating through the region. The number of such events or the presence of a long-duration illumination are open questions. Variability of the reflected emission all over of the central 300 pc, in particular in the 6.4 keV Fe Ka line, can bring strong constraints. To do so we performed a deep scan of the inner 300 pc with XMM-Newton in 2012. Together with all the archive data taken over the course of the mission, and in particular a similar albeit more shallow scan performed in 2000-2001, this allows for a detailed study of variability of the 6.4 keV line emission in the region, which we present here. We show that the overall 6.4 keV emission does not strongly vary on average, but variations are very pronounced on smaller scales. In particular, most regions showing bright reflection emission in 2000-2001 significantly decrease by 2012. We discuss those regions and present newly illuminated features. The absence of bright steady emission argues against the presence of an echo from an event of multi-centennial duration and most, if not all, of the emission can likely be explained by a limited number of relatively short (i.e. up to 10 years) events.

[94] arXiv:1712.04229v1 [pdf, vox]

Observational Constraint on Spherical Inhomogeneity with CMB and Local Hubble Parameter

Masato Tokutake, Kiyotomo Ichiki, Chul-Moon Yoo
Submitted Tuesday 12 December 2017 @ 11:05:11 GMT
5 figures, 12 pages

We derive an observational constraint on a spherical inhomogeneity of the void centered at our position from the angular power spectrum of the cosmic microwave background(CMB) and local measurements of the Hubble parameter. The late time behaviour of the void is assumed to be well described by the so-called $\Lambda$-Lema\^itre​-Tolman-Bondi~($\Lam​bda$LTB) solution. Then, we restrict the models to the asymptotically homogeneous models each of which is approximated by a flat Friedmann-Lema\^itre​-Robertson-Walker model. The late time $\Lambda$LTB models are parametrized by four parameters including the value of the cosmological constant and the local Hubble parameter. The other two parameters are used to parametrize the observed distance-redshift relation. Then, the $\Lambda$LTB models are constructed so that they are compatible with the given distance-redshift relation. Including conventional parameters for the CMB analysis, we characterize our models by seven parameters in total. The local Hubble measurements are reflected in the prior distribution of the local Hubble parameter. As a result of a Markov-Chains-Monte-​Carlo analysis for the CMB temperature and polarization anisotropies, we found that the inhomogeneous universe models with vanishing cosmological constant are ruled out as is expected. However, a significant under-density around us is still compatible with the angular power spectrum of CMB and the local Hubble parameter.

[95] arXiv:1712.04222v1 [pdf, vox]

MAORY science cases white book

G. Fiorentino, M. Bellazzini, P. Ciliegi, G. Chauvin, S. Douté, V. D'Orazi, E. Maiorano, F. Mannucci, M. Mapelli, L. Podio, P. Saracco, M. Spavone
Submitted Tuesday 12 December 2017 @ 10:48:57 GMT
169 pages, pdf file. Also available at the MAORY Science page: http://wwwmaory.oabo​.inaf.it/index.php/s​cience-pub/

MAORY is the Adaptive Optic (AO) module that will be installed at the E-ELT at the first light of the telescope. It will provide two different types of AO correction, a very high correction over a small FoV (diameter ~10 arcsec, SCAO mode) and a moderate and homogeneous correction over a wide FoV (diameter ~60 arcsec, MCAO mode). Here we present a first collection of science cases for MAORY feeding the E-ELT first light camera and spectrograph MICADO. Since the general science cases for E-ELT have already been developed elsewhere, here we focus on the design of specific observations, to explore the capabilities and observing modes of the system.

[96] arXiv:1712.04219v1 [pdf, vox]

Exploiting simultaneous multi-frequency observations to probe polar-cap processes

Yogesh Maan
Submitted Tuesday 12 December 2017 @ 10:38:46 GMT
2 pages, 1 figure, Proceedings IAU Symposium No. 337 Pulsar Astrophysics - The Next 50 Years

Sub-pulse drifting has been regarded as one of the most insightful aspects of the pulsar radio emission. The phenomenon is generally explained with a system of emission sub-beams rotating around the magnetic axis, originating from a carousel of sparks near the pulsar surface (the carousel model). Since the observed radio emission at different frequencies is generated at different altitudes in the pulsar magnetosphere, corresponding sampling of the carousel on the polar cap differs slightly in magnetic latitude. When this aspect is considered, it is shown here that the carousel model predicts important observable effects in multi-frequency or wide-band observations. Also presented here are brief mentions of how this aspect can be exploited to probe the electrodynamics in the polar cap by estimating various physical quantities, and correctly interpret various carousel related phenomena, in addition to test the carousel model itself.

[97] arXiv:1712.04215v1 [pdf, vox]

The physics of protoplanetesimal dust agglomerates. X. High-velocity collisions between small and large dust agglomerates as growth barrier

Rainer Schräpler, Jürgen Blum, Sebastiaan Krijt, Jan-Hendrik Raabe
Submitted Tuesday 12 December 2017 @ 10:31:34 GMT

In a protoplanetary disk, dust aggregates in the $\mu$m to mm size range possess mean collision velocities of 10 to 60 ms$^{-1}$ with respect to dm- to m-size bodies. We performed laboratory collision experiments to explore this parameter regime and found a size- and velocity-dependent threshold between erosion and growth. By using a local Monte Carolo coagulation calculation and complementary a simple semi-analytical timescale approach, we show that erosion considerably limits particle growth in protoplanetary disks and leads to a steady-state dust-size distribution from $\mu$m to dm sized particles.

[98] arXiv:1712.04209v1 [pdf, vox]

Magnetic Activity in the Galactic Centre Region -- Fast Downflows along Rising Magnetic Loops

Kensuke Kakiuchi, Takeru K. Suzuki, Yasuo Fukui, Kazufumi Torii, Mami Machida, Ryoji Matsumoto
Submitted Tuesday 12 December 2017 @ 10:22:48 GMT
Submitted to MNRAS. 9 pages, 12 figures

We studied roles of the magnetic field on the gas dynamics in the Galactic bulge by a three-dimensional global magnetohydrodynamica​l simulation data, particularly focusing on vertical flows that are ubiquitously excited by magnetic activity. In local regions where the magnetic filed is stronger, fast downflows with speed of ~ 100 km/s are triggered near the footpoint of magnetic loops that are buoyancy risen by Parker instability. These downward flows are accelerated by the vertical component of the gravity, falling along inclined field lines, which we call magnetic sliding slopes. The two footpoints of rising magnetic loops are generally located at different radial locations and the field lines are deformed by the differential rotation. The angular momentum is transported along the field lines, and the radial force balance breaks down. As a result, a fast downflow is often observed only at the one footpoint located at the inner radial position. The fast downflow compresses the gas to form a dense region near the footpoint, which will be important in star formation afterward. Furthermore, the azimuthal and radial components of the velocity are also excited, which are observed as high velocity features in a simulated position-velocity diagram. Depending on the viewing angle, these fast flows will show a large variety of characteristic features in the position-velocity diagram.

[99] arXiv:1712.04204v1 [pdf, vox]

Enhancing the H2O Megamaser Detection Rate Using Optical and Mid-infrared Photometry

C. Y. Kuo, A. Constantin, J. A. Braatz, H. H. Chung, C. A. Witherspoon, C. M. V. Impellizzeri, F. Gao, L. Hao, J. -H. Woo, I. Zaw
Submitted Tuesday 12 December 2017 @ 10:15:37 GMT
22 pages, 3 tables, 10 figures. Submitted to ApJ

Water megamasers from circumnuclear disks in galaxy centers provide the most accurate measurements of supermassive black hole masses and uniquely probe the sub-parsec accretion processes. At the same time, these systems offer independent crucial constraints of the Hubble Constant in the nearby universe, and thus, the arguably best single constraint on the nature of dark energy. The chances of finding these golden standards are however abysmally low, at an overall ~<3% for any level of water maser emission detected at 22 GHz, and ~<1% for those exhibiting the disk-like configuration. We provide here a thorough summary of the current state of the detection of water megamaser disks, along with a novel investigation of the chances of increasing their detection rates based on a multivariate parameter analysis of optical and mid-infrared photometric properties of the largest database of galaxies surveyed for the 22 GHz emission. We find that galaxies with water megamaser emission tend to associate with strong emission in all WISE mid-infrared wavelengths, with the strongest enhancement in the W4 band, at 22 micron, as well as with previously proposed and newly found indicators of AGN strength in the mid-infrared, such as red W1-W2 and W1-W4 colors, and the integrated mid-infrared luminosity of the host galaxy. While these trends offer a potential boost of the megamaser detection rates to 6 - 15%, or a factor of 2-8 relative to the current rates, depending on the chosen sample selection criteria, the completeness rate remains generally low (40 -- 60% of megamasers would not be targeted). By combining criteria of mid-IR brightness, optical colors, and the optical brightness, the detection rate of disk masers can be effectively boosted to ~> 6%, with ~> 60% completeness rates.

[100] arXiv:1712.04203v1 [pdf, vox]

Magnetospheric Gamma-Ray Emission in Active Galactic Nuclei

Grigorios Katsoulakos, Frank M. Rieger
Submitted Tuesday 12 December 2017 @ 10:14:33 GMT
13 pages, 2 figures, ApJ in press

The rapidly variable, very high-energy (VHE) gamma-ray emission from Active Galactic Nuclei (AGN) has been frequently associated with non-thermal processes occurring in the magnetospheres of their supermassive black holes. The present work aims to explore the adequacy of different gap-type (unscreened electric field) models to account for the observed characteristics. Based on a phenomenological description of the gap potential, we estimate the maximum extractable gap power $L_{gap}$ for different magnetospheric set-ups, and study its dependence on the accretion state of the source. $L_{gap}$ is found to be in general proportional to the Blandford-Znajek jet power $L_{BZ}$ and a sensitive function of gap size $h$, i.e. $L_{gap} \sim L_{BZ} (h/r_g)^{\beta}$, where the power index $\beta \geq 1$ is dependent on the respective gap-setup. The transparency of the black hole vicinity to VHE photons generally requires a radiatively inefficient accretion environment and thereby imposes constraints on possible accretion rates, and correspondingly on $L_{BZ}$. Similarly, rapid variability, if observed, may allow to constrain the gap size $h\sim c \Delta t$. Combining these constraints, we provide a general classification to assess the likelihood that the VHE gamma-ray emission observed from an AGN can be attributed to a magnetospheric origin. When applied to prominent candidate sources these considerations suggest that the variable (day-scale) VHE activity seen in the radio galaxy M87 could be compatible with a magnetospheric origin, while such an origin appears less likely for the (minute-scale) VHE activity in IC310.

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