@book{gledocs_11858_00-1735-0000-0001-30C4-C, author = {Krumpe, Mirko}, title = {X-ray and optical properties of X-ray luminous active galactic nuclei}, year = {2008}, publisher = {Univ. Potsdam}, abstract = {Giacconi et al. (1962) discovered a diffuse cosmic X-ray background with rocket experiments when they searched for lunar X-ray emission. Later satellite missions found a spectral peak in the cosmic X-ray background at ~30 keV. Imaging X-ray satellites such as ROSAT (1990-1999) were able to resolve up to 80% of the background below 2 keV into single point sources, mainly active galaxies. The cosmic X-ray background is the integration of all accreting super-massive (several million solar masses) black holes in the centre of active galaxies over cosmic time. Synthesis models need further populations of X-ray absorbed active galaxy nuclei (AGN) in order to explain the cosmic X-ray background peak at ~30 keV. Current X-ray missions such as XMM-Newton and Chandra offer the possibility of studying these additional populations...}, note = { \url {http://hdl.handle.net/11858/00-1735-0000-0001-30C4-C}}, }