Volume 526, February 2011
|Number of page(s)||6|
|Published online||05 January 2011|
Letters to the Editor
The XMM Deep survey in the CDF-S
I. First results on heavily obscured AGN⋆,⋆⋆
INAF – Osservatorio Astronomico di Bologna,
via Ranzani 1,
2 Dipartimento di Astronomia, Università di Bologna, via Ranzani 1, 40127 Bologna, Italy
3 ICREA and Institut de Ciències del Cosmos, Universitat de Barcelona (IEEC-UB), Martí i Franqués 1, 08028 Barcelona, Spain
4 Instituto de Física de Cantabria (CSIC-UC), Avenida de los Castros, 39005 Santander, Spain
5 Department of Astronomy and Astrophysics, 525 Davey Lab, the Pennsylvania State University, University Park, PA 16802, USA
6 Institute for Gravitation and the Cosmos, The Pennsylvania State University, University Park, PA 16802, USA
7 Max-Planck-Institut für extraterrestrische Physik, Giessenbachstrasse 1, 85748 Garching bei München, Germany
8 University of Maryland, Baltimore County, 1000 Hilltop Circle, Baltimore, MD 21250, USA
9 Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138, USA
10 INAF – Osservatorio Astronomico di Roma, via Frascati 33, 00040 Monteporzio Catone, Italy
11 Max-Planck-Institut für Plasmaphysik, Boltzmannstrasse 2, 85748 Garching bei München, Germany
12 European Southern Observatory, Karl-Schwarzschild-Strasse 2, 85748 Garching bei München, Germany
13 Dipartimento di Scienze Fisiche, Università di Napoli “Federico II”,V. Cinthia 9, 80126 Napoli, Italy
14 ASI Science Data Center, via Galileo Galilei, 00044 Frascati, Italy
15 Institute for the Physics and Mathematics of the Universe (IPMU), IPMU, University of Tokyo, Kashiwanoha 5-1-5, Kashiwa Chiba 277-8568, Japan
16 INAF – Osservatorio Astronomico di Trieste, via Tiepolo 11, 34143 Trieste, Italy
17 Pontificia Universidad Católica de Chile, Departamento de Astronomía y Astrofísica, Casilla 306, Santiago 22, Chile
Received: 10 November 2010
Accepted: 16 December 2010
We present the first results of the spectroscopy of distant, obscured AGN as obtained with the ultra-deep (≈3.3 Ms) XMM-Newton survey in the Chandra deep field South. One of the primary goals of the project is to characterize the X-ray spectral properties of obscured and heavily obscured Compton-thick AGN over the range of redhifts and luminosities that are relevant in terms of their contribution to the X-ray background. The ultra-deep exposure, coupled with the XMM detector’s spectral throughput, allowed us to accumulate good quality X-ray spectra for a large number of X-ray sources and, in particular, for heavily obscured AGN at cosmological redshifts. Specifically we present the X-ray spectral properties of two high-redshift – z = 1.53 and z = 3.70 – sources. The XMM spectra of both are very hard, with a strong iron Kα line at a rest-frame energy of ~6.4 keV. A reflection-dominated continuum provides the best description of the X-ray spectrum of the z = 1.53 source, while the intrinsic continuum of the z = 3.70 AGN is obscured by a large column NH ≈ 1024 cm-2 of cold gas. Compton-thick absorption, or close to it, is unambiguously detected in both sources. Interestingly, these sources would not be selected as candidate Compton thick AGN by some multiwavelength selection criteria based on the mid-infrared to optical and X-ray to optical flux ratios.
Key words: galaxies: active / galaxies: high-redshift / X-rays: galaxies / X-rays: diffuse background
This work is based on observations obtained with XMM-Newton, an ESA science mission with instruments and contributions directly funded by ESA Member States and the USA (NASA).
Table 1 is only available in electronic form at http://www.aanda.org
© ESO, 2011
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