Computer simulations of environmental influences on galaxy evolution in dense clusters. II - Rapid tidal encounters

Abstract

To assess the significance for galaxy morphological evolution of rapid tidal encounters in dense galaxy cluster cores, a direct N-body simulation of the passage of a flat disk galaxy through the core of a cD cluster is performed. The disk galaxy is modeled by 1,000 softened point stars rotating in the spherical potential of a stabilizing Plummer halo. Ambient cluster galaxies are modeled by means of Plummer spheres. It is found that the collisions resulting from a single cluster traversal inflict serious disruption in the outer galaxy disk but leave the galaxy nuclear regions essentially unperturbed. It is noted that if the disks of spiral galaxies form by accretion from extended gaseous envelopes over long time scales, such rapid tidal encounters may arrest disk development through the disruption and dissipation of the envelope. It is suggested through the simulation that only the flattest of elliptical galaxies could be created from disk systems through repeated collisional heating, except perhaps in the cores of the densest clusters where the encounter frequency is very high.