Large-scale structures in the distribution of X-ray selected AGN

Proceedings of the Conference "Highlights in X-ray Astronomy" held in Garching, 17-19 June 1998,
Eds. B. Aschenbach, M. Freyberg, MPE-Report No. 272, pp. 218 - 221

D.Engels [1], F. Tesch [1], C. Ledoux [2], J. Wei [3], A. Ugryumov [4], D. Valls-Gabaud [2], J. Hu [3], W. Voges [5]

  1. Hamburger Sternwarte, Gojenbergsweg 112, D-21029 Hamburg, Germany
  2. Observatoire Astronomique de Strasbourg, 11 Rue de l'Universite, F-67000 Strasbourg, France
  3. Beijing Astronomical Observatory, Chinese Academy of Sciences, Beijing 100080, P.R. China
  4. Special Astrophysical Observatory, RAS, Nizhnij Arkhyz, Karachai-Circessia, Russia
  5. Max-Planck-Institut für extraterrestrische Physik, Giessenbachstrasse, D-85740 Garching, Germany

Abstract

We are searching for large-scale structures in the distribution of AGN discovered by the ROSAT All-Sky Survey. The RASS detected >60000 X-ray objects, of which ~35% are AGN at z<0.5. The surface density in the extragalactic sky is ~0.5 AGN/deg**2, which has not been reached until now by any other survey for this redshift range. We efficiently single out the AGN among all the RASS sources using the Hamburg/RASS database of optical identifications, which contains presently 13867 entries. Follow-up spectroscopy of RASS AGN candidates identified in selected areas of the northern sky is underway to determine the spatial distribution of the AGN in these areas. In every area structures reminiscent of clusters and filaments are found on scales 50 - 100 h^-1 Mpc. These structures have a similar size as the serendipitously discovered groups of AGN in optical surveys at higher redshifts. Samples of low redshift AGN drawn from the RASS are large enough to be used with samples of higher redshift to study evolutionary effects in the large-scale distribution of AGN.

Contact: Dieter Engels.

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