Jonathan TRUMP
(Steward Observatory)
I will present a summary of results from the spectroscopic survey of X-ray and IR selected AGN in COSMOS using the Magellan/IMACS and MMT/Hectospec instruments. These observations reveal the strongest evidence to date for redshift evolution in the obscured fraction of
AGN, as well as the well-known luminosity dependence. These observed effects show that much of AGN obscuration must be driven by the host galaxy, particularly suggesting that dusty star formation in the host galaxy obscures the broad line region of their resident AGN. COSMOS is also ideal for finding low accretion rate AGN: I will show that Type 1 AGN have a minimum accretion rate, below which the broad line region becomes invisible. A set of ~50 X-ray bright, optically dull AGN in our survey also indicates that most of these objects are probably normal AGN diluted by their host galaxies. However ~1/3 of optically dull AGN appear to be intrinsically weak in optical emission, suggesting that they may be radiatively inefficient accretors. I will summarize how these results change the ``unified model'' of AGN fueling and obscuration.