Volume 433, Number 3, April III 2005
|Page(s)||855 - 873|
|Published online||29 March 2005|
X-ray spectra of XMM-Newton serendipitous medium flux sources
Instituto de Física de Cantabria (CSIC-UC), 39005 Santander, Spain
2 Department of Physics and Astronomy, University of Leicester, LE1 7RH, UK e-mail: email@example.com
3 Osservatorio Astronomico di Brera, via Brera 28, 20121 Milano, Italy
4 Astrophysikalisches Institut Potsdam, An der Sternwarte 16, 14482 Potsdam, Germany
5 Mullard Space Science Laboratory, UCL, Holmbury St Mary, Dorking, Surrey RH5 6NT, UK
Accepted: 14 December 2004
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 ~3.5 and contains 1137 sources with ~ 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 ~ of the sources with column densities in the range . The fraction of absorbed Narrow Emission Line galaxies (NELGs, most with intrinsic X-ray luminosities >, 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 , with intrinsic dispersion of 0.4. A small fraction (~) 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 0.3 keV. Comparing our results on absorption to popular X-ray background synthesis models, we find absorption in only ~ of the sources expected. This is due to a deficiency of heavily absorbed sources (with ) in our sample in comparison with the models. We therefore conclude that the synthesis models require some revision in their specific parameters.
Key words: X-rays: general / surveys / galaxies: active
© ESO, 2005
Current usage metrics show cumulative count of Article Views (full-text article views including HTML views, PDF and ePub downloads, according to the available data) and Abstracts Views on Vision4Press platform.
Data correspond to usage on the plateform after 2015. The current usage metrics is available 48-96 hours after online publication and is updated daily on week days.
Initial download of the metrics may take a while.