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High Energy Large Area Surveys: from BeppoSAX to Chandra and XMM

F. Fiore·A. Comastri·F. La Franca·C. Vignali·G. Matt·G. C. Perola
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Abstract

Optical identification of hard X-ray selected BeppoSAX and Chandra sources indicates that a large fraction of the sources are ``intermediate'' AGN, i.e. type 1.8-1.9 AGN, broad-line quasars and even X-ray loud but optically dull (apparently normal) galaxies, all obscured in X-rays by columns of the order of logNH=22-23.5 cm-2. Because of this obscuring matter, these sources are more difficult to detect or select at other wavelengths, implying that a fraction of the accretion power in the Universe may have been missed so far.

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F. Fiore, A. Comastri, F. La Franca, C. Vignali, G. Matt, G. C. Perola. 2001-02-02. High Energy Large Area Surveys: from BeppoSAX to Chandra and XMM. https://doi.org/10.1007/10854354_73

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