The XMM-Newton Wide-Field Survey in the COSMOS Field. II. X-Ray Data and the logN-logS Relations
Abstract
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 deg2 within the region of sky bounded by 09h57m30s<R.A.<10h03m30s, 01deg27'30''<decl.<02deg57'30'' 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 7.2×10-16 ergs cm-2 s-1, 4.0×10-15 ergs cm-2 s-1, and 9.7×10-15 ergs cm-2 s-1, 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.- Publication:
-
The Astrophysical Journal Supplement Series
- Pub Date:
- September 2007
- DOI:
- 10.1086/516586
- arXiv:
- arXiv:astro-ph/0701196
- Bibcode:
- 2007ApJS..172..341C
- Keywords:
-
- Cosmology: Observations;
- Cosmology: Dark Matter;
- Galaxies: Evolution;
- Galaxies: Formation;
- Cosmology: Large-Scale Structure of Universe;
- Surveys;
- Astrophysics
- E-Print:
- 12 Pages, 10 figures. Accepted for publication for the COSMOS APJS