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Paper: Infrared Properties of AGN in the GOODS Fields: AGN in Stellar Dominated High-z Galaxies
Volume: 357, The Spitzer Space Telescope: New Views of the Cosmos
Page: 286
Authors: Van Duyne, J.; Urry, C.M.; Chatzichristou, E.; Treister, E.; the GOODS AGN Team
Abstract: We present analysis of spectral energy distributions (SEDs) from mid-infrared through X-ray of a sample of 420 hard X-ray selected, z-band and Spitzer/IRAC detected active galactic nuclei (AGN) and AGN candidates from the GOODS multiwavelength survey. We fit local empirical SED templates of both normal and active galaxies to the rest-frame luminosities calculated from spectroscopic (where available) and photometric redshifts. The majority of the optically stellar-dominated (with early-type galaxy fits) sources are moderately luminous (LX,2−10keV 1043 erg/s) hard X-ray sources with high X-ray hardness ratios (H R > 0.2), high MIR luminosities and red MIR colors in excess of a typical stellar dominated elliptical galaxy. These sources likely harbor heavily obscured (though Compton-thin) AGN. The observed ratio of obscured to unobscured AGN has an integrated mean of ∼ 3.4 : 1 but declines with increasing redshift. This effect has been explained by Treister et al. (2004) as an observational bias triggered by the lack of spectroscopic redshifts at R > 24 which are predominantly higher redshift obscured sources.
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