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OATS-DAUT SEMINAR
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Speaker: Meg Urry (Yale University)

Title: Supermassive Black Holes in Deep Surveys

Date: Wednesday, October 25th, 2006
Time: 11:00
Venue: Villa Bazzoni

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Abstract:
In principle, counting Active Galactic Nuclei (AGN) reveals the demographics of supermassive black holes. Optical/UV surveys easily find AGN out to high redshift, and they are numerous in the early Universe (z~2-3); however, if obscuration is important, as suggested by local AGN unification and by the spectrum of the X-ray background, the true number could be much larger. Using the deepest data from the Spitzer, Hubble, and Chandra Observatories, the Great Observatories Origins Deep Survey (GOODS) project reveals evidence for a substantial population of obscured AGN, with which we can explain the integrated X-ray background, the redshift distributions in deep X-ray surveys, and the infrared number counts of AGN. We can also directly estimate the AGN contribution to the extragalactic infrared background. With the larger-area MUSYC survey, we extend this work to higher luminosity AGN, and we report the discovery of new EXOs (Extreme X-ray Objects). Finally, combining all the large, deep, multiwavelength surveys, we find that the fraction of obscured AGN increases with redshift.
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