Galaxies 09: Assembly, Gas Content and Star Formation History of Galaxies
Gregory Snyder
Harvard-Smithsonian Center for Astrophysics
Poststarburst Galaxies in Merger Simulations
Poststarburst (or ``E+A") galaxies, defined by a recently truncated burst of star formation as determined from optical spectral lines, are prime testing grounds for the merger hypothesis. Local E+A galaxies are most likely objects transforming from gas-rich disks to passively evolving, early-type galaxies as the result of galaxy interactions. In addition, since we expect it to appear shortly after the bright AGN phase in major mergers, the poststarburst phase offers a unique opportunity to study the post-merger effects of quasar and star formation feedback on the remaining gas reservoir. We present our efforts to model E+A galaxies using fully three-dimensional numerical simulations of galaxy mergers. We find that merging gas-rich disks of nearly equal mass on a variety of orbits can produce the optical features of a poststarburst galaxy. We discuss whether galaxy mergers can account for the population of E+As found in spectroscopic surveys. We compare our poststarburst models to observations in various wavelength regimes in an attempt to understand the properties of any remaining gas and its star-formation history. Specifically, we test whether our models can produce the E+A signature while highly obscured star formation continues. We describe what our models say about the poststarburst phenomenon at higher redshifts, and consider how JWST might be used to select $z > 1$ counterparts to nearby E+A galaxies. We assess the role of ALMA and the EVLA in detecting and characterizing the remaining gas content, and Herschel for determining the importance of dust-enshrouded star formation. We highlight how such observations might be used to advance our knowledge of the relationship between mergers, star formation, and galaxy evolution.
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