8th HEAD Meeting, 8-11 September, 2004
Session 3 Surveys and the Cosmic X-ray Background
Poster, Wednesday, September 8, 2004, 9:00am-10:00pm

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[3.03] The history of the density of Active Galactic Nuclei

F. La Franca (Dipartimento di Fisica, Universita` Roma Tre), HELLAS2XMM Collaboration

We present the measure of the cosmological evolution of the density of AGN and their NH distribution up to redshift 4, as a function of the unabsorbed 2-10 keV luminosity and redshift. We used the new 2-10 keV HELLAS2XMM sample combined with other published 2-10 keV catalogs. A total of about 500 AGN have been used. Our best fit is a luminosity dependent density evolution (LDDE) model. The data show a significant increase of the fraction of absorbed (LogNH>22) AGN at low X-ray luminosities. A less significant increase of the fraction of absorbed AGN at high reshift is also found. Our best fit solution provides a god fit to a) the cosmic X-ray background; b) the observed counts; and c) the observed fraction of absorbed AGN as a function of the flux.

The author(s) of this abstract have provided an email address for comments about the abstract: lafranca@fis.uniroma3.it

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Bulletin of the American Astronomical Society, 36 #3
© 2004. The American Astronomical Soceity.