Welcome to the BAHAMAS project

(FYI - BAHAMAS stands for BAryons and HAloes of MAssive Systems)

What is the BAHAMAS project?
BAHAMAS is a first attempt to do large-scale structure (LSS) cosmology using self-consistent full cosmological hydrodynamical simulations. Such simulations simultaneously follow all of the important matter components and allow us to accurately address the main uncertainty in the theoretical modelling of LSS, which is astrophysical effects (such as feedback) associated with the baryonic component.

A lay person's description of the project can be found in an article put together by LJMU's media team.

The initial BAHAMAS paper, which describes in detail our feedback modelling strategy, is McCarthy et al. (2017).

With a viable model for astrophysical effects, we are now gearing up to explore variations in cosmology. Both in the context of the standard model (LCDM), but also plausible extensions of LCDM, including massive neutrino cosmologies, time-variable dark energy models, and modified gravity models.

Recently, we posted our initial results on constraints on the summed mass of neutrinos in McCarthy et al. (2018). A popular science article about our results can be found in The Conversation.


LJMU groupLeiden group
Ian McCarthy (PI, staff)
Andreea Font (staff)
Juliana Kwan (postdoc, starting 09/18)
Jaime Salcido (postdoc, starting 09/18)
Ben Mummery (PhD student)
Egidijus Kukstas (PhD student)
Simon Pfeifer (PhD student)
Alberto Acuto (PhD student)
you? (PhD student - hiring)
Joop Schaye
Mathieu Schaller (postdoc)
Marcel van Daalen (postdoc)
Stijn Debackere (PhD student)

Simeon Bird, Johns Hopkins / UC Riverside
Scott Kay, Manchester
Ludovic van Waerbeke, UBC
Joachim Harnois-Deraps, Edinburgh
Amandine Le Brun, CEA Saclay
Gus Evrard, Michigan
Arya Farahi, Michigan
Hideki Tanimura, Orsay
Andrew Robertson, Durham
Baojiu Li, Durham
David Harvey, EPFL


Simulated maps from McCarthy+2018:
  • thermal Sunyaev-Zel'dovich (tSZ) effect maps
  • galaxy weak lensing convergence and shear maps
  • CMB weak lensing convergence maps (appropriate for cross-correlations with other "low-z" maps only)

    The above maps are stored in FITS files. They all have the same dimensions: 5 deg x 5 deg with 10 arcsec pixels (1800x1800 pixels) and are integrated back to z=3. There are 25 maps for each simulation, derived from 25 quasi-independent light cones. Particles are mapped to a grid using a simple 'nearest grid point' method. See McCarthy et al. 2018 for details of the map-making process.

    For galaxy weak lensing maps, the array stored in the FITS files is a 3x1800x1800 array, where [0,*,*] corresponds to the convergence map ('kappa'), [1,*,*] corresponds to the first component of the reduced shear ('g1'), and [2,*,*] corresponds to the second component of the reduced shear ('g2'). Lensing maps for the CFHTLens revisited (Joudaki+2017) and KiDS 450 (Hildebrandt+2017) analyses are provided and constructed using the source redshift distributions obtained from the CFHTLenS and KiDS websites. If you would like BAHAMAS weak lensing maps for an alternative source redshift distribution, please contact Ian McCarthy.


  • Multi-wavelength scaling relations in galaxy groups: a detailed comparison of GAMA and KiDS observations to BAHAMAS simulations
    Jakobs, A., Viola, M., McCarthy, I. G., et al. 2018, MNRAS, submitted (arXiv:1712.05463)

  • Localized massive halo properties in BAHAMAS and MACSIS simulations: scalings, log-normality, and covariance
    Farahi, A., Evrard, A. E., McCarthy, I. G., Barnes, D. J., Kay, S. T., 2018, MNRAS, in press (arXiv:1711.04922)

  • A search for warm/hot gas filaments between pairs of SDSS Luminous Red Galaxies
    Tanimura, H., Hinshaw, G., McCarthy, I. G., et al. 2017, MNRAS, submitted (arXiv:1709.05024)

  • The BAHAMAS project: the CMB--large-scale structure tension and the roles of massive neutrinos and galaxy formation
    McCarthy, I. G., Bird, S., Schaye, J., Harnois-Deraps, J., Font, A. S., van Waerbeke, L., 2018, MNRAS, 476, 2999

  • A detection of wobbling brightest cluster galaxies within massive galaxy clusters
    Harvey, D., Courbin, F., Kneib, J. P., & McCarthy, I. G. 2017, MNRAS, 472, 1972

  • The separate and combined effects of baryon physics and neutrino free streaming on large-scale structure
    Mummery, B. O., McCarthy, I. G., Bird, S., & Schaye, J. 2017, MNRAS, 471, 227

  • The impact of baryons on massive galaxy clusters: halo structure and cluster mass estimates
    Henson, M. A., Barnes, D. J., Kay, S. T., McCarthy, I. G., & Schaye, J. 2017, MNRAS, 465, 3361

  • The redshift evolution of massive galaxy clusters in the MACSIS simulations
    Barnes, D. J., Kay, S. T., Henson, M. A., McCarthy, I. G., Schaye, J., & Jenkins, A. 2017, MNRAS, 465, 213

  • The BAHAMAS project: calibrated hydrodynamical simulations for large-scale structure cosmology
    McCarthy, I. G., Schaye, J., Bird, S., & Le Brun, A. M. C. 2017, MNRAS, 465, 2936

  • Cosmology with velocity dispersion counts: an alternative to measuring cluster halo masses
    Caldwell, C. E., McCarthy, I. G., Baldry, I. K., Collins, C. A., Schaye, J., & Bird, S. 2016, MNRAS, 462, 4117