[38.03] The Spitzer View of X-ray--selected AGN, X-ray--faint AGN, and Lensed Sub-mm Galaxies

AAS 207th Meeting, 8-12 January 2006
Session 38 The X-ray and Infrared Backgrounds, AGN Evolution
Oral, Monday, 10:00-11:30am, January 9, 2006, Delaware A

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[38.03] The Spitzer View of X-ray--selected AGN, X-ray--faint AGN, and Lensed Sub-mm Galaxies

J. R. Rigby, G. H. Rieke, J. L. Donley (Univ. of Arizona), A. Alonso-Herrero (CSIC), P. G. Pérez-González (Univ. of Arizona)

First, I'll discuss studies of X-ray--selected AGN in the Chandra Deep Field South, using deep Spitzer and Chandra data. In particular, I'll discuss why 20% of X-ray--selected AGN are "optically--faint" (answer: They're redder and at higher redshift (median z=1.6) than most X-ray--selected AGN); why half of X-ray--selected AGN lack optical AGN lines (answer: They tend to lie in inclined disk galaxies, such that the host galaxy has obscured their narrow line regions); and whether the ratio of mid-IR to hard X-ray luminosities in AGN depends on column density (answer: No, not at z=1 or z=0.)

Second, I'll summarize our searches for distant AGN using Spitzer: about half the sources we're finding are missed by deep X-ray surveys. Some of these might be the hypothesized highly--obscured "Compton--thick" AGN.

Third, I will discuss results from a sample of sub-millimeter galaxies that have been lensed by foreground galaxy clusters. I will present 0.4--24 micron spectral energy distributions, using photometry from Hubble (ACS and WFPC2) and Spitzer (IRAC and MIPS), which allows a detailed looks at the redshifts, stellar masses, stellar populations, and AGN contribution of these galaxies.

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