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Astronomy Tea Talks at Caltech

Mondays, Robinson 106
Tea:  4.00pm
Talk: 4.15pm

Organized by:

2008 - 2009 season:
23 September 2008
Jonathan Trump (Tucson)

"Fueling and Obscuration of Faint and Low-Mass AGN in COSMOS"

The Cosmic Evolution Survey (COSMOS) provides a unique opportunity for
the study of AGN with a combination of deep radio (VLA), infrared
(Spitzer MIPS & IRAC), optical (Hubble/ACS & 21-band
Subaru/Suprime-Cam), UV (GALEX), and X-ray (XMM & Chandra)
observations over 2 deg2. I will present results from a 3-year
spectroscopic survey of X-ray and IR selected AGN in COSMOS using the
Magellan/IMACS and MMT/Hectospec instruments. This spectroscopic
sample reaches the customary quasar/Seyfert luminosity boundary at
z~2, and also reveals Type 1 AGN with black hole masses of only 10^7
M_sun to z~2. The IR selection additionally allows us to observe a
large number of heavily obscured AGN, which recent pencil-beam surveys
have revealed to be a significant fraction of the total AGN
population. The obscured fraction of AGN in COSMOS shows the
well-known luminosity dependence, but also shows the most significant
evidence to date for redshift evolution. These dependencies suggest a
strong case for dusty star formation driving AGN obscuration, with
luminous AGN luminosity providing negative feedback. COSMOS also
allows for new constraints on fueling mechanisms of obscured and
unobscured AGN. A large sample of Type 1 AGN allows us to suggest
limits on accretion rate for the presence of a stable BLR. And the
largest sample of X-ray bright / optical normal galaxies (XBONGs) to
date, complete with bolometric SEDs, suggests that these targets are
actually radiatively inefficient accretors with truncated accretion
disks. I will try to place these ideas in the framework of the AGN
unified model and discuss how they might be especially tested with
future Herschel and ALMA observations.

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Last modified on 20th Jul 2011 by Scott Schnee.  

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