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The evolution of the density of galaxy clusters and groups: denser environments at higher redshifts

Poggianti, Bianca M. and De Lucia, Gabriella and Varela, Jesus and Aragón-Salamanca, Alfonso and Finn, Rose and Desai, Vandana and von der Linden, Anja and White, Simon D. M. (2010) The evolution of the density of galaxy clusters and groups: denser environments at higher redshifts. Monthly Notices of the Royal Astronomical Society, 405 (2). pp. 995-1005. ISSN 0035-8711.

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We show that, observationally, the projected local density distribution in high-z clusters is shifted towards higher values compared to clusters at lower redshift. To search for the origin of this evolution, we analyse a sample of haloes selected from the Millennium simulation and populated using semi-analytic models, investigating the relation between observed projected density and physical three-dimensional (3D) density, using densities computed from the 10 and three closest neighbours. Both observationally and in the simulations, we study the relation between number of cluster members and cluster mass, and the number of members per unit of cluster mass. We find that the observed evolution of projected densities reflects a shift to higher values of the physical 3D density distribution. In turn, this must be related with the globally higher number of galaxies per unit of cluster volume N/V in the past. We show that the evolution of N/V is due to a combination of two effects: (i) distant clusters were denser in dark matter (DM) simply because the DM density within R_(200) (~ the cluster virial radius) is defined to be a fixed multiple of the critical density of the Universe, and (ii) the number of galaxies per unit of cluster DM mass is remarkably constant both with redshift and cluster mass if counting galaxies brighter than a passively evolving magnitude limit. Our results highlight that distant clusters were much denser environments than today's clusters, both in galaxy number and mass, and that the density conditions felt by galaxies in virialized systems do not depend on the system mass.

Item Type:Article
Related URLs:
URLURL TypeDescription
Poggianti, Bianca M.0000-0001-8751-8360
Aragón-Salamanca, Alfonso0000-0001-8215-1256
Finn, Rose0000-0001-8518-4862
Desai, Vandana0000-0002-1340-0543
Additional Information:© 2010 The Authors. Journal compilation © 2010 RAS. Accepted 2010 February 17. Received 2010 January 26; in original form 2009 November 17. We thank Andrea Biviano and Erica Ellingson for useful comments. BMP thanks the Alexander von Humboldt Foundation and the Max-Planck Instituut fur Extraterrestrische Physik in Garching for a very pleasant and productive staying during which the work presented in this paper was carried out. The MS data bases used in this paper and the web application providing online access to them were constructed as part of the activities of the German Astrophysical Virtual Observatory. BMP acknowledges financial support from ASI contract I/016/07/0. GDL acknowledges financial support from the European Research Council under the European Community’s Seventh Framework Programme (FP7/2007-2013)/ERC grant agreement n. 202781.
Group:Infrared Processing and Analysis Center (IPAC)
Funding AgencyGrant Number
Agenzia Spaziale Italiana (ASI)I/016/07/0
European CommunityFP7/2007-2013
European Research Council (ERC)202781
Subject Keywords:galaxies: clusters: general; galaxies: evolution; galaxies: interactions; galaxies: statistics
Issue or Number:2
Record Number:CaltechAUTHORS:20100629-165511683
Persistent URL:
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:18865
Deposited By: Jason Perez
Deposited On:30 Jun 2010 18:06
Last Modified:28 Oct 2019 20:21

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