Properties of galaxies in rich clusters

We present a model to investigate the formation and evolution of cluster galaxies using cosmological high-resolution N-body simulations. The N-body simulations are used to construct merging history trees of galactic dark halos. Gas cooling, star formation, supernova feedback and mergers of galaxies within dark halos are included by using simple prescriptions taken from semi-analytic models of galaxy formation. Using this method, we represent the morphology-density relation for simulated cluster galaxies and the color-magnitude relation of simulated cluster ellipticals under the major merger-driven bulge formation scenario. We find that this morphological evolution model gives a good explanation for the distribution and colors of the cluster ellipticals, while it cannot reproduce the distribution of S0 galaxies. These results suggest that the elliptical galaxies are mainly formed by the major mergers and the processes other than major mergers play important role in the S0 formation.