Morphology-Density Relation for Simulated Clusters of Galaxies in Cold   Dark Matter Dominated Universe
  We present a model to investigate the formation and evolution of cluster galaxies using cosmological N-body simulations. The N-body simulations are used to make merging history trees of 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. In this {\it Letter} we exam the merger-driven bulge formation model and represent the morphology-density relation of cluster galaxies at z = 0. We find that this morphological evolution model can explain the distribution of elliptical galaxies in the clusters well and cannot reproduce the distribution of S0 galaxies. This result suggests that the elliptical galaxies are mainly formed by the major mergers, while, in the S0 formation, the processes other than major mergers play important role. 
Takashi Okamoto and Masahiro Nagashima