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A. Comastri (INAF-Osservatorio Astronomico Bologna)
Deep hard X-ray surveys have resolved a significant fraction of the hard X-ray background into individual sources. Despite intensive multiwavelength follow-up observations a sizable fraction of hard X-ray sources (presumably the most obscured and at high redshift) remain unidentified. I will discuss several approches developed by our team (the HELLAS2XMM collaboration) to investigate the nature of these sources and the consequences for the study of their space density and evolution as well as for the modelling of the hard X-ray background. I will also discuss the need for X--ray observations above 10 keV to search for the sources of the hard X-ray background close to the peak of its emission (30 keV).
The author(s) of this abstract have provided an email address for comments about the abstract: andrea.comastri@bo.astro.it
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Bulletin of the American Astronomical Society, 36 #3
© 2004. The American Astronomical Soceity.