Recent Dynamical Evolution of Galaxy Clusters

Abstract

Evidence is presented for the recent evolution of the relaxation processes in clusters of galaxies, using large optical and X-ray cluster samples. The criteria of the cluster relaxation used are the cluster ellipticity, the intracluster medium (ICM) temperature, and X-ray cluster luminosity. We find evidence of varying strength and significance of all three indicators evolving with redshift for z 0.15. This result supports the view that clusters have mostly stopped undergoing mergers and accreting matter, as expected in a low-Ωm universe, and are now in the process of gravitational relaxation, which reduces their flattening, their ICM temperature (shock heated during the merging phase), and their X-ray luminosity. These results support similar recent claims of Melott, Chambers, & Miller.