Evolution of Late-type Galaxies in a Cluster Environment: Effects of
  High-speed Multiple Encounters with Early-type Galaxies
  Late-type galaxies falling into a cluster would evolve being influenced by
the interactions with both the cluster and the nearby cluster member galaxies.
Most numerical studies, however, tend to focus on the effects of the former
with little work done on those of the latter. We thus perform a numerical study
on the evolution of a late-type galaxy interacting with neighboring early-type
galaxies at high speed, using hydrodynamic simulations. Based on the
information obtained from the Coma cluster, we set up the simulations for the
case where a Milky Way-like late-type galaxy experiences six consecutive
collisions with twice as massive early-type galaxies having hot gas in their
halos at the closest approach distances of 15-65 kpc/h at the relative
velocities of 1500-1600 km/s. Our simulations show that the evolution of the
late-type galaxy can be significantly affected by the accumulated effects of
the high-speed multiple collisions with the early-type galaxies, such as on
cold gas content and star formation activity of the late-type galaxy,
particularly through the hydrodynamic interactions between cold disk and hot
gas halos. We find that the late-type galaxy can lose most of its cold gas
after the six collisions and have more star formation activity during the
collisions. By comparing our simulation results with those of galaxy-cluster
interactions, we claim that the role of the galaxy-galaxy interactions on the
evolution of late-type galaxies in clusters could be comparable with that of
the galaxy-cluster interactions, depending on the dynamical history.
