Astronomy and Astrophysics, volume 433, 855-873 (2005/4-3)
X-ray spectra of XMM-Newton serendipitous medium flux sources.
MATEOS S., BARCONS X., CARRERA F.J., CEBALLOS M.T., CACCIANIGA A., LAMER G., MACCACARO T., PAGE M.J., SCHWOPE A. and WATSON M.G.
Abstract (from CDS):
We report on the results of a detailed analysis of the X-ray spectral properties of a large sample of sources detected serendipitously with the XMM-Newton observatory in 25 selected fields, for which optical identification is in progress. The survey covers a total solid angle of ∼3.5deg2 and contains 1137 sources with ∼10–15<S0.5–10<10–12erg/cm2/s with good enough spectral quality as to perform a detailed X-ray spectral analysis of each individual object. We find evidence for hardening of the average X-ray spectra of the sources towards fainter fluxes, and we interpret this as indicating a higher degree of photoelectric absorption amongst the fainter population. Absorption is detected at 95% confidence in 20% of the sources, but it could certainly be present in many other sources below our detection capabilities. For Broad Line AGNs (BLAGNs), we detect absorption in ∼10% of the sources with column densities in the range 1021-1022cm–2. The fraction of absorbed Narrow Emission Line galaxies (NELGs, most with intrinsic X-ray luminosities >1043erg/s, and therefore classified as type 2 AGNs) is significantly higher (40%), with a hint of moderately higher columns. After correcting for absorption, we do not find evidence for a redshift evolution of the underlying power law index of BLAGNs, which stays roughly constant at Γ∼1.9, with intrinsic dispersion of 0.4. A small fraction (∼7%) of BLAGNs and NELGs require the presence of a soft excess, that we model as a black body with temperature ranging from 0.1 to 0.3keV. Comparing our results on absorption to popular X-ray background synthesis models, we find absorption in only ∼40% of the sources expected. This is due to a deficiency of heavily absorbed sources (with NH∼1022-1024cm–2) in our sample in comparison with the models. We therefore conclude that the synthesis models require some revision in their specific parameters.
X-rays: general - surveys - galaxies: active
Table 1 some objects not identified (incomplete format). XMMU J33106.2+241325, XMMU J12226.1+752616, XMMU J13316.2+241326, XMMU J233113.6+20056, XMMU J122312.6+75247 not identified (incomplete format. Comple te format = XMMU JHHMMSS.s+DDMMSS).
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