28 September 2006

Speaker: Christy Tremonti (University of Arizona)

Title: Post-starburst Galaxies and Fossil Galactic Winds: new constraints on feedback and the starburst-AGN connection

Abstract: 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 post-starburst galaxies at z =0.1-1. These objects are the likely remnants of major mergers, observed a few hundred million years after the peak of their star formation and QSO activity. In a large fraction of post-starbursts we detect absorption lines from the interstellar medium which are blueshifted by by 200 - 2000 km/s with respect to the stars. We hypothesize that the absorbing material represents a fossil starburst/AGN wind launched near the peak of the galaxy's starburst and AGN activity. We use stellar population synthesis models to estimate the time since the last major burst, and we use this timescale in conjunction with the measured wind velocity to estimate the distance of the absorbing material from the galaxy and the energy needed to power such a wind. We find evidence for on-going low-level AGN activity in a majority of post-starburst galaxies, and we explore the degree to which star formation and black hole accretion are correlated. We consider the implications of these observations for the feedback-limited growth of galaxies and black holes, and for the pollution of the intergalactic medium.

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