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Paper: Compton-Thick AGN in the SWIRE/Chandra Survey
Volume: 381, The Second Annual Spitzer Science Center Conference: Infrared Diagnostics of Galaxy Evolution
Page: 434
Authors: Polletta, M.; Wilkes, B.J.; Siana, B.; Lonsdale, C.J.; Kilgard, R.; Shupe, D.L.; Surace, J.; Smith, H.E.; Kim, D.-W.; Owen, F.
Abstract: Using the large multi-wavelength data set in the Chandra/SWIRE Survey (0.6 square degrees in the Lockman Hole), we show evidence for the existence of highly obscured (Compton-thick) AGN, estimate a lower limit to their surface density and characterize their multi-wavelength properties. Two independent selection methods based on the X-ray and infrared spectral properties are presented. The two selected samples contain 1) 5 X-ray sources with hard Xray spectra and column densities ≥1024 cm−2, and 2) 120 infrared sources with red and AGN-dominated infrared spectral energy distributions (SEDs). We estimate a surface density of at least 25 Compton-thick AGN per square degree detected in the IR in the Chandra/SWIRE field of which about 40% show distinct AGN signatures in their optical/near-infrared SEDs, the remainings being dominated by the host-galaxy emission. Only 33% of all Compton-thick AGN are detected in the X-rays at our depth (F(0.3-8 keV)> 10−15 erg cm−2 s−1).

We report the discovery of two sources in our sample of Compton-thick AGN, SWIRE J104409.95+585224.8 (z=2.54) and SWIRE J104406.30+583954.1 (z=2.43), which are the most luminous Compton-thick AGN at high-z currently known. The properties of these two sources are discussed in detail with an analysis of their spectra, SEDs, luminosities and black-hole masses.

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