The Symbiotic Relationship Between the Evolution of Galaxy Groups and Their Resident Galaxies

Abstract

The vast majority of galaxies reside in groups and it is becoming increasingly clear that much of the transformation of galaxies occurs in this intermediate environment rather than in larger clusters. We report on observational and analytical work that shows how the evolution of the group environment influences the evolution of the resident galaxies and how feedback resulting from the evolution of individual galaxies influences their larger environment. In particular, the dynamical assembly of groups is marked by an increase in galaxy–galaxy interactions and mergers that ultimately result in a group with a significant population of elliptical galaxies and a diffuse X-ray halo. The infall of baryons into the group produces a hot intragroup medium whose temperature can be maintained by episodic AGN feedback.