Evolution of Late-type Galaxies in a Cluster Environment: Effects of High-speed Multiple Encounters with Early-type Galaxies

TL;DR

This study uses hydrodynamic simulations to show that high-speed, multiple encounters with early-type galaxies significantly influence the evolution of late-type galaxies in clusters, affecting their gas content and star formation.

Contribution

It is the first to numerically analyze the cumulative effects of high-speed galaxy-galaxy encounters on late-type galaxy evolution within clusters.

Findings

Late-type galaxies can lose most of their cold gas after multiple high-speed collisions.

Star formation activity can increase during galaxy-galaxy collisions.

Galaxy-galaxy interactions can be as influential as cluster-wide effects on galaxy evolution.

Abstract

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.