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Maria del Carmen Polletta et al. 2006 ApJ 642 673 doi:10.1086/500821

Chandra and Spitzer Unveil Heavily Obscured Quasars in the Chandra/SWIRE Survey*

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Maria del Carmen Polletta1, Belinda J. Wilkes2, Brian Siana3,4, Carol J. Lonsdale1,5, Roy Kilgard2, Harding E. Smith1,4, Dong-Woo Kim2, Frazer Owen4,6, Andreas Efstathiou7, Tom Jarrett5, Gordon Stacey8, Alberto Franceschini9, Michael Rowan-Robinson10, Tom S. R. Babbedge10, Stefano Berta9, Fan Fang3, Duncan Farrah8, Eduardo González-Solares11, Glenn Morrison4,12, Jason A. Surace3 and Dave L. Shupe3

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Abstract References Cited By

Using the large multiwavelength data set in the Chandra/SWIRE Survey (0.6 deg2 in the Lockman Hole), we show evidence for the existence of highly obscured (Compton-thick) AGNs, estimate a lower limit to their surface density, and characterize their multiwavelength properties. Two independent selection methods based on the X-ray and infrared spectral properties are presented. The two selected samples contain (1) five X-ray sources with hard X-ray spectra and column densities gtrsim1024 cm-2 and (2) 120 infrared sources with red and AGN-dominated infrared SEDs. We estimate a surface density of at least 25 Compton-thick AGNs deg-2 detected in the infrared in the Chandra/SWIRE field, of which ~40% show distinct AGN signatures in their optical/near-infrared SEDs, the remaining being dominated by the host galaxy emission. Only ~33% of all Compton-thick AGNs are detected in the X-rays at our depth [F(0.3-8 keV) > 10-15 ergs cm-2 s-1]. We report the discovery of two sources in our sample of Compton-thick AGNs, SWIRE J104409.95+585224.8 (z = 2.54) and SWIRE J104406.30+583954.1 (z = 2.43), which are the most luminous Compton-thick AGNs 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.


Footnote
*  Some of the data presented herein were obtained at the W. M. Keck Observatory, which is operated as a scientific partnership among the California Institute of Technology, the University of California, and the National Aeronautics and Space Administration. The Observatory was made possible by the generous financial support of the W. M. Keck Foundation. Based on observations at the Kitt Peak National Observatory, National Optical Astronomy Observatory, which is operated by the Association of Universities for Research in Astronomy, Inc., under cooperative agreement with the National Science Foundation. The National Radio Astronomy Observatory is a facility of the National Science Foundation operated under a cooperative agreement by Associated Universities, Inc.
Subject headings

galaxies: active; infrared: galaxies; quasars: individual (SWIRE J104409.95+585224.8, SWIRE J104406.30+583954.1); X-rays: galaxies


Dates

Issue 2 (2006 May 10)

Received 2005 September 10, accepted for publication 2005 December 21



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