The XMM deep survey in the CDF-S

III. Point source catalogue and number counts in the hard X-rays^⋆,⋆⋆

¹ Institute for Astronomy, Astrophysics, Space Applications and Remote Sensing, National Observatory of Athens, Palaia Penteli, 15236 Athens, Greece
e-mail: piero.ranalli@oabo.inaf.it
² INAF – Osservatorio Astronomico di Bologna, via Ranzani 1, 40127 Bologna, Italy
³ Università di Bologna, Dipartimento di Fisica e Astronomia, via Berti Pichat 6/2, 40127 Bologna, Italy
⁴ Instituto de Física de Cantabria (CSIC – UC), 39005 Santander, Spain
⁵ ASI Science Data Center, via Galileo Galilei, 00044 Frascati, Italy
⁶ Department of Astronomy and Astrophysics, Pennsylvania State University, University Park, PA 16802, USA
⁷ Institute for Gravitation and the Cosmos, Pennsylvania State University, University Park, PA 16802, USA
⁸ Max –Planck – Institut für extraterrestrische Physick, 85478 Garching, Germany
⁹ ICREA and Institut de Ciències del Cosmos (ICC), Universitat de Barcelona, (IEEC – UB), Martí y Franquès 1, 08028 Barcelona, Spain
¹⁰ ESO, Karl-Schwarschild-Strasse 2, 85748 Garching bei Munchen, Germany

Received: 31 January 2013
Accepted: 17 April 2013

Abstract

Nuclear obscuration plays a key role in the initial phases of AGN growth, yet not many highly obscured active galactic nuclei (AGN) are currently known beyond the local Universe, and their search is an active topic of research. The XMM-Newton survey in the Chandra Deep Field South (XMM-CDFS) aims at detecting and studying the spectral properties of a significant number of obscured and Compton-thick (N_H ≳ 10²⁴ cm^-2) AGN. The large effective area of XMM-Newton in the 2–10 and 5–10 keV bands, coupled with a 3.45 Ms nominal exposure time (2.82 and 2.45 Ms after light curve cleaning for MOS and PN, respectively), allows us to build clean samples in both bands, and makes the XMM-CDFS the deepest XMM-Newton survey currently published in the 5–10 keV band. The large multi-wavelength and spectroscopic coverage of the CDFS area allows for an immediate and abundant scientific return. In this paper, we present the data reduction of the XMM-CDFS observations, the method for source detection in the 2–10 and 5–10 keV bands, and the resulting catalogues. A number of 339 and 137 sources are listed in the above bands with flux limits of 6.6 × 10^-16 and 9.5 × 10^-16 erg s^-1 cm^-2, respectively. The flux limits at 50% of the maximum sky coverage are 1.8 × 10^-15 and 4.0 × 10^-15 erg s^-1 cm^-2, respectively. The catalogues have been cross-correlated with the Chandra ones: 315 and 130 identifications have been found with a likelihood-ratio method, respectively. A number of 15 new sources, previously undetected by Chandra, is found; 5 of them lie in the 4 Ms area. Redshifts, either spectroscopic or photometric, are available for  ~ 95% of the sources. The number counts in both bands are presented and compared to other works. The survey coverage has been calculated with the help of two extensive sets of simulations, one set per band. The simulations have been produced with a newly-developed simulator, written with the aim of the most careful reproduction of the background spatial properties. For this reason, we present a detailed decomposition of the XMM-Newton background into its components: cosmic, particle, and residual soft protons.The three components have different spatial distributions. The importance of these three components depends on the band and on the camera; the particle background is the most important one (80–90% of the background counts), followed by the soft protons (4–20%).