LoCuSS: connecting the dominance and shape of brightest cluster galaxies with the assembly history of massive clusters
Abstract
We study the luminosity gap, ∆m_(12), between the first- and second-ranked galaxies in a sample of 59 massive (~10^(15)M_⊙) galaxy clusters, using data from the Hale Telescope, the Hubble Space Telescope, Chandra and Spitzer. We find that the ∆m_(12) distribution, p(∆m_(12)), is a declining function of ∆m_(12) to which we fitted a straight line: p(∆m_(12))∝−(0.13 ± 0.02)∆m_(12). The fraction of clusters with 'large' luminosity gaps is p(∆m_(12) ≥ 1) = 0.37 ± 0.08, which represents a 3σ excess over that obtained from MonteCarlo simulations of a Schechter function that matches the mean cluster galaxy luminosity function. We also identify four clusters with 'extreme' luminosity gaps, ∆m_(12) ≥ 2, giving a fraction of p(∆m_(12) ≥ 2) = 0.07^(+0.05)_(−0.03). More generally, large luminosity gap clusters are relatively homogeneous, with elliptical/discy brightest cluster galaxies (BCGs), cuspy gas density profiles (i.e. strong cool cores), high concentrations and low substructure fractions. In contrast, small luminosity gap clusters are heterogeneous, spanning the full range of boxy/elliptical/discy BCG morphologies, the full range of cool core strengths and dark matter concentrations, and have large substructure fractions. Taken together, these results imply that the amplitude of the luminosity gap is a function of both the formation epoch and the recent infall history of the cluster. 'BCG dominance' is therefore a phase that a cluster may evolve through and is not an evolutionary 'cul-de-sac'. We also compare our results with semi-analytic model predictions based on the Millennium Simulation. None of the models is able to reproduce all of the observational results on ∆m_(12), underlining the inability of the current generation of models to match the empirical properties of BCGs. We identify the strength of active galactic nucleus feedback and the efficiency with which cluster galaxies are replenished after they merge with the BCG in each model as possible causes of these discrepancies.
Additional Information
© 2010 The Authors. Journal compilation © 2010 RAS. Accepted 2010 July 6. Received 2010 July 2; in original form 2009 October 21. Article first published online: 6 Oct. 2010. We acknowledge helpful comments from the anonymous referee. We thank our LoCuSS collaborators, in particular Alastair Edge, Victoria Hamilton-Morris, Jean-Paul Kneib, Yuying Zhang and Nobuhiro Okabe, for encouragement, assistance and many stimulating discussions. HGK, GPS, AJRS, TJP and JPS acknowledge support from PPARC and latterly from STFC. GPS acknowledges support from the Royal Society. GPS thanks Andrew Benson, Richard Bower, Gabriella de Lucia and Malcolm Bremer for helpful discussions and comments; Kevin Bundy, Brad Cenko, Chris Conselice, Richard Ellis, Avishay Gal-Yam, Sean Moran, David Sand and Keren Sharon for assistance with acquiring some of the nearinfrared data presented in this paper; and Rick Burruss and Jeff Hickey for their support at Palomar Observatory.Attached Files
Published - Smith2010p12113Mon_Not_R_Astron_Soc.pdf
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Additional details
- Eprint ID
- 21732
- Resolver ID
- CaltechAUTHORS:20110112-115635152
- Particle Physics and Astronomy Research Council (PPARC)
- Science and Technology Facilities Council (STFC)
- Royal Society
- Created
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2011-01-12Created from EPrint's datestamp field
- Updated
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2021-11-09Created from EPrint's last_modified field