2004/01/29 by C. R. Mullis, A. Vikhlinin, J. P. Henry +6 · 3 citations
Physics and Astronomy · #Astronomy and Astrophysical Research #Astrophysical Phenomena and Observations #Galaxies: Formation, Evolution, Phenomena #astro-ph
paper · pdf · doi:10.1086/383234
published as Astrophys.J. 607 (2004) 175-189 · 15 pages, 10 figures, accepted for publication in ApJ
arxiv created 2004/01/29 · openalex publication_date 2004/05/17 · arxiv updated 2009/12/01 · openalex created_date 2016/06/24 · openalex updated_date 2026/07/31
We report measurements of the cluster X-ray luminosity function out to z = 0.8 based on the final sample of 201 galaxy systems from the 160 Square Degree ROSAT Cluster Survey. There is little evidence for any measurable change in cluster abundance out to z ~ 0.6 at luminosities of less than a few times 10 44 h ergs s -1 (0.5-2.0 keV). However, for 0.6 < z < 0.8 and at luminosities above 10 44 h ergs s -1 , the observed volume densities are significantly lower than those of the present-day population. We quantify this cluster deficit using integrated number counts and a maximum likelihood analysis of the observed luminosity-redshift distribution fit with a model luminosity function. The negative evolution signal is more than 3 σ regardless of the adopted local luminosity function or cosmological framework. Our results and those from several other surveys independently confirm the presence of evolution. Whereas the bulk of the cluster population does not evolve, the most luminous and presumably most massive structures evolve appreciably between z = 0.8 and the present. Interpreted in the context of hierarchical structure formation, we are probing sufficiently large mass aggregations at sufficiently early times in cosmological history, when the universe has yet to assemble these clusters to present-day volume densities.