X-ray Source Counts in the XMM-COSMOS Survey

We present the analysis of the source counts in the XMM-COSMOS survey using data of the first year of XMM-Newton observations. The survey covers∼2 deg within the region of sky bounded by 957.5 < R.A. < 1003.5; 127.5 < DEC < 257.5 with a total net integration time of 504 ks. Using a maximum likelihood algorithm we detected a total of 1390 sources at least in one band. Using Monte Carlo simulations to estimate the sky coverage we produced the logN-logS relations. These relations have been then derived in the 0.5–2 keV, 2–10 keV and 5–10 keV energy bands, down to flux limits of 7.2×10 erg cm s, 4.0×10 erg cm s and 9.7×10 erg cm s, respec tively. These relations have been compared to previous X-ray survey and to the most recent X-ray background model finding an excellent agreement. The slightly different normalizations observed in t he source counts of COSMOS and previous surveys can be largely explained as a co mbination of low counting statistics and cosmic variance introduced by the large scale structure.