Back to Volume
Paper: Detecting Obscured AGN in the Distant Universe with Spitzer
Volume: 380, At the Edge of the Universe: Latest Results from the Deepest Astronomical Surveys
Page: 119
Authors: Donley, J.L.; Rieke, G.H.; Perez-Gonzalez, P.G.; Rigby, J.R.; Alonso-Herrero, A.
Abstract: We present the results of a Spitzer search for obscured AGN in the Chandra Deep Field-North, using both radio-excess and mid-infrared power-law selection. AGN selected via the former technique tend to lie at z ~ 1, have SEDs dominated by the 1.6 μm stellar bump, and have Seyfert-like X-ray luminosities (when detected in the X-ray). In contrast, the IRAC (3.6-8.0 μm) power-law selected AGN lie at higher redshifts of z ~ 2 and comprise a significant fraction of the most X-ray luminous AGN in the CDF-N. While there is almost no overlap in the AGN samples selected via these two methods, their X-ray detection fractions are very similar. Only 40% and 55% of the radio-excess and power-law samples are detected in the 2 Ms X-ray catalog, respectively. The majority of the AGN selected via both methods are consistent with being obscured (NH > 1022 cm−2), but not Compton-thick (NH > 1024 cm−2), although Compton-thick candidates exist in both samples. We place an upper limit of ≤ 82% (or ≤ 4 : 1) on the obscured fraction of the power-law sample, consistent with predictions from the cosmic X-ray background. The sources selected via the power-law criteria comprise a subset of AGN selected via other IRAC color-color cuts. While smaller in number than the color-selected samples in the deep fields, the power-law sample suffers from less contamination by star-forming galaxies.
Back to Volume