The XMM-Newton Wide-Field Survey in the COSMOS Field. II. X-Ray Data and the logN-logS Relations

We present data analysis and X-ray source counts for the first season of XMM-Newton observations in the COSMOS field. The survey covers ~2 deg<SUP>2</SUP> within the region of sky bounded by 09<SUP>h</SUP>57<SUP>m</SUP>30<SUP>s</SUP><R.A.<10<SUP>h</SUP>03<SUP>m</SUP>30<SUP>s</SUP>, 01<SUP>deg</SUP>27<SUP>'</SUP>30<SUP>''</SUP><decl.<02<SUP>deg</SUP>57<SUP>'</SUP>30<SUP>''</SUP> with a total net integration time of 504 ks. A maximum likelihood source detection was performed in the 0.5-2, 2-4.5, and 4.5-10 keV energy bands, and 1390 pointlike sources were detected in at least one band. Detailed Monte Carlo simulations were performed to fully test the source-detection method and to derive the sky coverage to be used in the computation of the logN-logS relations. These relations were then derived in the 0.5-2, 2-10, and 5-10 keV energy bands, down to flux limits of 7.2×10<SUP>-16</SUP> ergs cm<SUP>-2</SUP> s<SUP>-1</SUP>, 4.0×10<SUP>-15</SUP> ergs cm<SUP>-2</SUP> s<SUP>-1</SUP>, and 9.7×10<SUP>-15</SUP> ergs cm<SUP>-2</SUP> s<SUP>-1</SUP>, respectively. Thanks to the large number of sources detected in the COSMOS survey, the logN-logS curves are tightly constrained over a range of fluxes which were poorly covered by previous surveys, especially in the 2-10 and 5-10 keV bands. The 0.5-2 and 2-10 keV differential logN-logS relations were fitted with a broken power-law model which revealed a Euclidean slope at the bright end and a flatter slope (α~1.5) at faint fluxes. In the 5-10 keV energy band a single power law provides an acceptable fit to the observed source counts with a slope α~2.4. A comparison with the results of previous surveys shows good agreement in all the energy bands under investigation in the overlapping flux range. We also notice a remarkable agreement between our logN-logS relations and the most recent model of the X-ray background. Based on observations obtained with XMM-Newton, an ESA science mission with instruments and contributions directly funded by ESA Member States and NASA; also based on data collected at the Canada-France-Hawaii Telescope operated by the National Research Council of Canada, the Centre National de la Recherche Scientifique de France, and the University of Hawaii.