SIMBAD references

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 ≳10²⁴/cm2 and (2) 120 infrared sources with red and AGN-dominated infrared SEDs. We estimate a surface density of at least 25 Compton-thick AGNs/deg2 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/cm2/s]. 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.