The density and masses of obscured Black Holes

Abstract

Recent Chandra and XMM-Newton surveys have uncovered a large fraction of the obscured AGN responsible of the hard X-ray background. One of the most intriguing results of extensive programs of follow-up observations concerns the optical and near-infrared properties of the hard X-ray sources counterparts. More specifically, for a significant fraction of hard X-ray obscured sources the AGN responsible of the high X-ray luminosity remains elusive over a wide range of wavelengths from soft X-rays to near-infrared. This very observational result opens the possibility to investigate the host of bright obscured quasars in some detail. Here we briefly report on some preliminar results obtained for a small sample of elusive AGN in the HELLAS2XMM survey.

8 pages, 4 figures, to appear in the proceedings of the meeting "Baryons on Cosmic Structures", Roma, October 20-21, 2003

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• The Chandra-COSMOS survey IV: X-ray spectra of the bright sample
• The HELLAS2XMM survey. X. The bolometric output of luminous obscured quasars: The Spitzer perspective
• X-ray spectral analysis of optically faint sources in the Chandra Deep Fields
• The HELLAS2XMM survey. IX. Spectroscopic identification of super-EROs hosting AGNs
• Bulgeless Galaxies at Intermediate Redshift: Sample Selection, Colour Properties, and the Existence of Powerful AGN
• XMM Follow-Up Observations of Three Swift BAT-Selected Active Galactic Nuclei