Physics Colloquium

Wed, 11/14/2012 - 16:00 - 17:00
Meg Urry, Yale University
"The Interplay of Supermassive Black Hole Growth and Galaxy Evolution"

The growth of black holes over billions of years releases energy that may quench star formation and strongly affect galaxy evolution ("feedback"). Using multiwavelength surveys to trace the cosmic history of black hole growth at the centers of galaxies, we find that most Active Galactic Nuclei are heavily obscured, and thus are not found in large area optical surveys like the Sloan Digital Sky Survey, and that obscuration is more common in the young Universe and in moderate luminosity AGN. Most black hole growth takes place in these moderate luminosity AGN rather than in their higher luminosity counterparts ("quasars"), and feedback in such systems affects far more galaxies than do quasars. At the peak epoch of black hole growth and star formation (>5 billion years ago), we find evidence that AGN may help quench star formation (which is not the case in the local Universe). Perhaps surprisingly, most moderate luminosity AGN are hosted in galaxies with significant disks, even at the peak epoch, suggesting that major mergers do not trigger most black hole growth. Finally, we find an intriguing dependence of AGN activity on host galaxy morphology which is not yet fully explained.