<b>High Energy-Astrophysics</b><br><i>Structure Formation Up Close and Personal: Probing the Nature of Galaxy Subgroup Mergers with X-rays</i>

Speaker: Marie Machacek (Harvard/Smithsonian Center for Astrophysics)

Most galaxy evolution is found to occur in moderately massive galaxy groups, that, in hierarchical models of structure formation, may themselves be merging along filaments to form more massive large scale structures. For nearby examples of galaxy and subgroup mergers, the high angular resolution of the Chandra X-ray Observatory allows us to map the density, temperature, entropy and metal abundances in the galaxies and surrounding hot gas with unprecedented precision. Deep X-ray observations reveal sharp cold front edges, outflows, shocks, buoyant bubbles, and sweeping tails that chronicle the galaxy/gas motions, and the heating and chemical enrichment of the intragroup medium. Using several examples of nearby galaxy subgroup mergers, I will show how imaging and spectral analyses of these X-ray features constrain the kinematics of the merger, probe the dynamical processes for gas stripping, sloshing and entropy evolution in the sub-group gas, and test models for feedback and the coevolution of host galaxies with their central supermassive black holes.