0 Fe b 20 06 Chandra and Spitzer unveil heavily obscured quasars in the SWIRE / Chandra Survey 1

Using the large multi-wavelength data set in the Chandra/SWIRE Survey (0.6 deg 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 X-ray spectra and column densities & 10 cm, 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 deg detected in the infrared in the Chandra/SWIRE field of which ∼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 ergs cm s). 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. Subject headings: galaxies: active —quasars: individual (SWIRE J104409.95+585224.8, SWIRE J104406.30+583954.1) — infrared: galaxies — X-rays: galaxies 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. Center for Astrophysics & Space Sciences, University of California, San Diego, La Jolla, CA 92093, USA Harvard/Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138, USA Spitzer Science Center, California Institute of Technology, 100-22, Pasadena, CA 91125, USA Visiting astronomer, Kitt Peak National Observatory, National Optical Astronomy Observatories, operated by AURA Inc, under cooperative agreement with the National Science Foundation. Infrared Processing & Analyis Center, California Institute of Technology, 100-22, Pasadena, CA 91125, USA National Radio Astronomy Observatory, P.O. Box O, Socorro, NM 87801, USA School of Computer Science and Engineering, Cyprus