Building Up the Red-Sequence: The AGN-Starburst Connection

Type Conference Paper
Names Laura Trouille, C. Tremonti, R. Hickox
Proceedings Title Bulletin of the American Astronomical Society
Conference Name American Astronomical Society, AAS Meeting #218, #123.03
Volume 43
Date May 1, 2011
Short Title Building Up the Red-Sequence
Library Catalog NASA ADS
Abstract Post-starburst galaxies, also known as K+A or E+A galaxies because of the characteristic features in their spectra, have recently undergone an abrupt cessation of active star formation (within 20-500 Myr). This exceptional and rare stage in galaxy evolution is thought to occur during the transition from gas-rich, star-forming galaxies into early-types. While it is poorly understood what causes the abrupt end of their star formation, there is strong evidence that galaxy-galaxy tidal interactions or mergers trigger the starburst in many of these galaxies. This same mechanism for triggering intensive star formation may also cause strong fuelling onto a central supermassive black hole. By studying the evolution of the properties of post-starbursts, we obtain insights into the origin of the red-sequence and key properties of the AGN-starburst connection. The use of post-starbursts as probes is only now feasible with the advent of large optical spectroscopic surveys. Here we compare results from the 3000 SDSS DR7 post-starbursts at z 0.1 (for which 60 have associated archival Chandra data) and the 200 post-starbursts from the DEEP2, zCOSMOS, and OPTX surveys at z 0.9 (accompanied by deep Chandra imaging). A key benefit of studying post-starburst galaxies is that they are natural chronometers; detailed population synthesis modeling provides an estimate of the time since the peak star-formation event. In this study we address the following questions: 1) Does a visual inspection for near-neighbors and tidal disruptions in our low-redshift sample show a trend with post-starburst age? 2) Do post-starbursts move across optical emission-line diagnostic diagrams as they age and what does this tell us about the time-delay between starburst activity and AGN fueling? 3) Are post-starburst X-ray properties (for individually detected sources and on average via X-ray stacking) correlated with time since peak in star formation activity?
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