Collisions between galaxies were once thought to be an extremely rare occurrence in the universe. But, in the last couple of decades we have learned that galaxy collisions are neither random, nor unlikely. It is now believed that most galaxies, including our Milky Way, have experienced several significant collisions in their lifetime. In fact, a good deal of evidence suggests that galaxies are built up hierarchically, with collisional processes playing a major role in both early and continuing galaxy evolution. By taking galaxies far from near equilibrium, self-regulated states, collisions also provide unique laboratories for the study of the fundamental processes of galaxy formation and evolution. In this talk I will describe some highlights of the wealth of new information on how collisions restructure galaxies, stimulate vast amounts of star formation, and trigger the active galactic nucleus phenomenon.

ANL Physics Division Colloquium Schedule