The evolution of clusters of galaxies. II - Tidal stripping versus mergers as a function of richness

Abstract

A previously described Monte Carlo code has been improved and used to investigate the evolution of clusters of galaxies of different richness. With one important exception, results of the previous study are confirmed. Under a specific set of assumptions about cluster conditions at virialization, the simulations do account for a number of observed properties of clusters. In particular, starting with 85 percent of the cluster mass in the intracluster medium, roughly 25 percent of the simulations produced cD galaxies. This percentage is roughly independent of initial or final cluster richness. The dependence of the magnitude of the second-ranked galaxy (M2) on M2-M1 predicted by these simulations may disagree with observations. Although the frequency of formation of a massive galaxy by mergers is roughly independent of richness, the luminosity stripped from the galaxies varies roughly as N-squared (where N is the total number of galaxies) in the simulations. The relative importance of the cD halo (or intracluster light) is therefore a strong function of richness, consistent with observational claims and with the proposal that the central region of the cD is produced by mergers while the halo is produced by stripping.