The XMM-Newton wide-field survey in the COSMOS field

• Published in: Astronomy and astrophysics (Berlin) 2009-04, Vol.497 (2), p.635-648
• Main Authors: Cappelluti, N., Brusa, M., Hasinger, G., Comastri, A., Zamorani, G., Finoguenov, A., Gilli, R., Puccetti, S., Miyaji, T., Salvato, M., Vignali, C., Aldcroft, T., Böhringer, H., Brunner, H., Civano, F., Elvis, M., Fiore, F., Fruscione, A., Griffiths, R. E., Guzzo, L., Iovino, A., Koekemoer, A. M., Mainieri, V., Scoville, N. Z., Shopbell, P., Silverman, J., Urry, C. M.
• Format: Article
• Language: English
• Subjects: galaxies: active; large-scale structure of Universe; X-rays: diffuse background; X-rays: galaxies
• ISSN: 0004-6361; 1432-0746
• DOI: 10.1051/0004-6361/200810794

Context. The COSMOS survey is a multiwavelength survey aimed to study the evolution of galaxies, AGN and large scale structures. Within this survey XMM-COSMOS a powerful tool to detect AGN and galaxy clusters. The XMM-COSMOS is a deep X-ray survey over the full 2 deg2 of the COSMOS area. It consists of 55 XMM-Newton  pointings for a total exposure of ~1.5 Ms with an average vignetting-corrected depth of 40 ks across the field of view and a sky coverage of 2.13 deg2. Aims. We present the catalogue of point-like X-ray sources detected with the EPIC CCD cameras, the $\log N - \log S$ relations and the X-ray colour–colour diagrams. Methods. The analysis was performed using the XMM-SAS data analysis package in the 0.5–2 keV, 2–10 keV and 5–10 keV energy bands. Source detection has been performed using a maximum likelihood technique especially designed for raster scan surveys. The completeness of the catalogue as well as $\log N -\log S$ and source density maps have been calibrated using Monte Carlo simulations. Results. The catalogs contains a total of 1887 unique sources detected in at least one band with likelihood parameter det_ml $>10$. The survey, which shows unprecedented homogeneity, has a flux limit of ~$1.7\times 10 ^{-15}$ erg cm-2 s-1, ~$9.3 \times 10 ^{-15}$ erg cm-2 s-1  and ~$1.3 \times 10^{-14}$ erg cm-2 s-1  over 90% of the area (1.92 deg2) in the 0.5–2 keV, 2–10 keV and 5–10 keV energy band, respectively. Thanks to the rather homogeneous exposure over a large area, the derived $\log N - \log S$ relations are very well determined over the flux range sampled by XMM-COSMOS. These relations have been compared with XRB synthesis models, which reproduce the observations with an agreement of ~10% in the 5–10 keV and 2–10 keV band, while in the 0.5–2 keV band the agreement is of the order of ~20%. The hard X-ray colors confirmed that the majority of the extragalactic sources in a bright subsample are actually type I or type II AGN. About 20% of the sources have a X-ray luminosity typical of AGN ($L_{\rm X}> 10^{42}$ erg/s) although they do not show any clear signature of nuclear activity in the optical spectrum.