EDP Sciences
Free access
Issue
A&A
Volume 441, Number 2, October II 2005
Page(s) 417 - 434
Section Cosmology (including clusters of galaxies)
DOI http://dx.doi.org/10.1051/0004-6361:20042134


A&A 441, 417-434 (2005)
DOI: 10.1051/0004-6361:20042134

Luminosity-dependent evolution of soft X-ray selected AGN

New Chandra and XMM-Newton surveys
G. Hasinger1, T. Miyaji2 and M. Schmidt3

1  Max-Planck-Institut für extraterrestrische Physik, Postf. 1312, 85741 Garching, Germany
    e-mail: ghasinger@mpe.mpg.de
2  Department of Physics, Carnegie Mellon University, 5000 Forbes Avenue, Pittsburg, PA 15213, USA
    e-mail: miyaji@cmu.edu
3  California Institute of Technology, Pasadena, CA 91125, USA
    e-mail: mxs@astro.caltech.edu

(Received 7 October 2004 / Accepted 10 June 2005 )

Abstract
We present new results on the cosmological evolution of unabsorbed (type-1) active galactic nuclei (AGN) selected in the soft (0.5-2 keV) X-ray band. From a variety of ROSAT, XMM-Newton and Chandra surveys we selected a total of ~1000 AGN with an unprecedented spectroscopic and photometric optical/NIR identification completeness. For the first time we are able to derive reliable space densities for low-luminosity (Seyfert-type) X-ray sources at cosmological redshifts. The evolutionary behaviour of AGN shows a strong dependence on X-ray luminosity: while the space density of high-luminosity AGN reaches a peak around $z\sim 2$, similar to that of optically selected QSO, the space density of low-luminosity AGNs peaks at redshifts below z=1. This confirms previous ROSAT findings of a luminosity-dependent density evolution. Using a rigorous treatment of the optical identification completeness we are able to show that the space density of AGN with X-ray luminosities $L_{\rm x} < 10^{45}$ erg s-1 declines significantly towards high redshifts.


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

SIMBAD Objects



© ESO 2005

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.