EDP Sciences Journals List
Advanced Search
Subscriber Authentication Point
Home All issues Volume 479/1 Article
Free access article

Issue A&A
Volume 479, Number 1, February III 2008
Page(s) 283 - 300
Section Online catalogs and data
DOI http://dx.doi.org/10.1051/0004-6361:20077687



A&A 479, 283-300 (2008)
DOI: 10.1051/0004-6361:20077687

XMM-Newton observations of the Lockman Hole: X-ray source catalogue and number counts

H. Brunner1, N. Cappelluti1, G. Hasinger1, X. Barcons2, A. C. Fabian3, V. Mainieri1, 4, and G. Szokoly1

1  Max-Planck-Institut für extraterrestrische Physik, 85478 Garching, Germany
    e-mail: hbrunner@mpe.mpg.de
2  Instituto de Física de Cantabria (CSIC-UC), 39005 Santander, Spain
3  Institute of Astronomy, University of Cambridge, Madingley Road, Cambridge, CB3 0HA, UK
4  ESO,Karl-Schwarschild-Strasse 2, 85748 Garching, Germany

(Received 20 April 2007 / Accepted 27 November 2007)

Abstract
Context.The Lockman Hole field represents the sky area of lowest Galactic line-of-sight column density $N_{\rm H}=5.7 \times 10^{19}$ cm-2. It was observed by the XMM-Newton X-ray observatory in 18 pointings for a total of 1.16 Ms (raw EPIC pn observing time) constituting the deepest XMM-Newton exposure so far. After the removal of time intervals with high particle background, the final effective exposure was 637 ks.
Aims.We present a catalogue of the X-ray sources detected in the central 0.196 deg2 of the field and discuss the derived number counts and X-ray colours.
Methods.The analysis was performed using the XMM-SAS data analysis package version 6.0. The detection sensitivity and fraction of spurious detections was calibrated using Monte Carlo simulations.
Results.In the 0.5-2.0 keV band, a sensitivity limit (defined as the faintest detectable source) of $1.9 \times10^{-16}$ erg cm-2 s-1 was reached. The 2.0-10.0 keV band and 5.0-10.0 keV band sensitivity limits were $9\times10^{-16}$ erg cm-2 s-1 and $1.8\times10^{-15}$ erg cm-2 s-1, respectively. A total of 409 sources above a detection likelihood of 10 (3.9 sigma) were found within a radius of 15$\arcmin$ off the field centre, of which 340, 266, and 98 sources were detected in the soft, hard, and very hard bands, respectively. The number counts in each energy band are in close agreement with results from previous surveys and with the synthesis models of the X-ray background. Six percent of the Compton-thick source candidates have been selected from the X-ray colour-colour diagram. This fraction is consistent with the most recent predictions of X-ray background population synthesis models at our flux limits. We also estimated, for the first time, the $\log N-\log S$ relation for Compton-thick AGN.


Key words: surveys -- galaxies: active -- galaxies: quasars: general -- X-rays: galaxies -- X-rays: general



© ESO 2008


What is OpenURL?

The OpenURL standard is a protocol for transmission of metadata describing the resource that you wish to access. An OpenURL link contains article metadata and directs it to the OpenURL server of your choice. The OpenURL server can provide access to the resource and also offer complementary services (specific search engine, export of references...). The OpenURL link can be generated by different means.
  • If your librarian has set up your subscription with an OpenURL resolver, OpenURL links appear automatically on the abstract pages.
  • You can define your own OpenURL resolver with your EDPS Account. In this case your choice will be given priority over that of your library.
  • You can use an add-on for your browser (Firefox or I.E.) to display OpenURL links on a page (see http://www.openly.com/openurlref/). You should disable this module if you wish to use the OpenURL server that you or your library have defined.