case western reserve university



Can Quasars Quench Star Formation? New clues from the study of fossil galactic winds in post-starburst galaxies

Christy Tremonti (Steward Observatory, University of Arizona)

Feedback from massive stars and accreting black holes has proven to be a key ingredient in successful models of galaxy evolution. Yet much about the feedback process is still poorly understood due to a lack of direct observational constraints. To help remedy this, we are studying a population of massive post-starburst galaxies at z~0.6. These objects are the likely remnants of major mergers, observed a few hundred million years after the peak of their star formation and quasar activity. In a 2/3 of our sample we detect Mg II absorption lines that are blueshifted by 500 - 2000 km/s with respect to the stars. We hypothesize that the absorbing material represents a fossil galactic wind launched near the peak of the galaxy's activity. We estimate the mass and energy of the outflow and conclude that feedback from a quasar may have played a role in expelling the cool gas and quenching star formation. We consider the implications of these observations for the formation of early-type galaxies and the pollution of the intergalactic medium.