Morphology-density relation for simulated clusters of galaxies in cold dark matter-dominated universes

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 dark halos. Gas cooling, star formation, supernova feedback, and mergers of galaxies within dark halos are included by using simple prescriptions taken from semianalytic models of galaxy formation. In this paper, we examine 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, processes other than major mergers play an important role.