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arXiv:astro-ph/0001037 (astro-ph)
[Submitted on 4 Jan 2000 (v1), last revised 10 Jan 2000 (this version, v2)]

Title:The BeppoSAX High Energy Large Area Survey (HELLAS): a progress Report

Authors:A. Comastri, F. Fiore, C. Vignali, F. La Franca, G. Matt
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Abstract: The integrated emission of highly obscured AGN is expected to provide a major contribution to the X-ray energy density in the Universe: the X-ray background (XRB). The study of these objects is possible only at energies where the effects of absorption are less severe. For this reason we have carried out the BeppoSAX High Energy LLarge Area Survey in the hardest band (5-10 keV) accessible so far with imaging X-ray instruments. The source surface density at the survey limiting flux accounts for a significant fraction (20-30%) of the hard XRB. The X-ray data complemented by multiwavelength follow--up observations suggest that a large fraction of the hard sources are AGN and that X-ray absorption with column densities in the range 10^22-23.5 cm-2 is common among them. The great diversity in their optical-near-IR properties suggests that the optical appearance of obscured sources is a function of the X-ray luminosity. We briefly discuss the implications of these findings for the XRB models.
Comments: Invited talk, to appear in the Proceedings of the Conference: ``Large Scale Structure in the X-ray Universe" Santorini, Greece, 20-22 September 1999, 8 pages, 4 figures. Added references
Subjects: Astrophysics (astro-ph)
Cite as: arXiv:astro-ph/0001037
  (or arXiv:astro-ph/0001037v2 for this version)
  https://doi.org/10.48550/arXiv.astro-ph/0001037

Submission history

From: Andrea Comastri [view email]
[v1] Tue, 4 Jan 2000 15:53:10 UTC (38 KB)
[v2] Mon, 10 Jan 2000 13:42:48 UTC (38 KB)
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