2004/03/03 by C. Vignali, Vignali, C.
Physics and Astronomy · #Astrophysics (astro-ph) #FOS: Physical sciences #astro-ph
paper · pdf · doi:10.48550/arxiv.astro-ph/0403100
3 pages, to appear in the proceedings of the Tenth Marcel Grossman Meeting on General Relativity, Rio de Janeiro, Brazil (July 20-26, 2003)
arxiv created 2004/03/03 · arxiv updated 2009/12/01
Recent Chandra and XMM-Newton surveys have confirmed that the cosmic X-ray background is mostly due to accretion onto super-massive black holes, integrated over cosmic time. Here we review the results obtained from the photometric and spectroscopic follow-up observations of the 122 X-ray sources detected by the HELLAS2XMM 1dF Survey down to a 2-10 keV flux of ~10-14 erg cm-2 s-1. In particular, we focus on the multiwavelength properties of a few intriguing classes of X-ray sources: high X-ray-to-optical flux ratio sources, Type 2 quasars, and XBONGs.