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Paper: Exploring the Early Universe with XMM-Newton
Volume: 262, The High Energy Universe at Sharp Focus: Chandra Science
Page: 105
Authors: Lehmann, I.; Hasinger, G.; Murray, S. S.; Schmidt, M.
Abstract: The question of the X-ray background has been largely settled over the last 10 years using the ROSAT satellite. About 70-80 % of the soft X-ray background was resolved into discrete sources, which are mainly X-ray and optically unobscured AGNs (Quasars, Sy1). Furthermore we found already several obscured AGNs in deep ROSAT surveys, which are predicted by the population synthesis models for the X-ray background, based on the unified AGN schemes. However, deep X-ray surveys using Chandra and XMM- Newton allow to prove the reliability of these models, which seems to be still far from unique. Recent observations with Chandra and XMM-Newton have already resolved most of the hard background into discrete sources. The first deep XMM-Newton survey was performed in the Lockman Hole region, one of the best studied sky areas over a wide wavelength range. About 100 ksec good exposure time have been accumulated with the EPIC camera during the performance verification phase. We reach a limiting flux of 0.31 and 1.4 x 10=AF15 erg/cm2/s in the 0.5-2.0 and 2-10 keV energy bands. A significant number of X-ray sources show hard, probably intrinsically absorbed X-ray spectra. We discuss the X-ray, optical and infrared properties of these sources in comparison with the predictions of the recent X-ray background models.
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