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Description
We present a detailed spectral analysis of pointlike X-ray sources in the XMM-Newton COSMOS field. Our sample of 135 sources only includes those that have more than 100 net counts in the 0.3-10keV energy band and have been identified through optical spectroscopy. The majority of the sources are well described by a simple power-law model with either no absorption (76%) or a significant intrinsic, absorbing column (20%). The remaining ~4% of the sources require a more complex modeling by incorporating additional components to the power law. For sources with more than 180 net counts (bright sample), we allowed both the photon spectral index Gamma and the equivalent hydrogen column NH to be free parameters. For fainter sources, we fix Gamma to the average value and allow NH to vary. The mean spectral index of the 82 sources in the bright sample is <Gamma>=2.06+/-0.08, with an intrinsic dispersion of ~0.24. Each of these sources has fractional errors on the value of Gamma below 20%. As expected, the distribution of intrinsic absorbing column densities is markedly different between AGNs with or without broad optical emission lines. We find within our sample four type 2 QSO candidates (L_X_>10^44^erg/s, NH>10^22^cm^-2^), with a spectral energy distribution well reproduced by a composite Seyfert 2 spectrum, that demonstrates the strength of the wide-field COSMOS XMM-Newton survey to detect these rare and underrepresented sources. In addition, we have identified a Compton-thick (NH>1.5x10^24^cm^-2^) AGN at z=0.1248. Its X-ray spectrum is well fitted by a pure reflection model and a significant Fe K{alpha} line at rest-frame energy of 6.4keV.
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