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.
