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The X‐ray background and the AGN X‐ray luminosity function
Author(s) -
Hasinger G.
Publication year - 1998
Publication title -
astronomische nachrichten
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.394
H-Index - 63
eISSN - 1521-3994
pISSN - 0004-6337
DOI - 10.1002/asna.2123190120
Subject(s) - physics , astrophysics , x ray background , rosat , supermassive black hole , galaxy , active galactic nucleus , astronomy , luminosity function , redshift , luminosity , accretion (finance) , black hole (networking) , population , computer network , routing protocol , routing (electronic design automation) , demography , sociology , computer science , link state routing protocol
ROSAT deep and shallow surveys have provided an almost complete inventory of the constituents of the soft X‐ray background which led to a population synthesis model for the whole X‐ray background with interesting cosmological consequences. According to this model the X‐ray background is the “echo” of mass accretion onto supermassive black holes, integrated over cosmic time. A new determination of the soft X‐ray luminosity function of active galactic nuclei (AGN) is inconsistent with pure luminosity evolution. The comoving volume density of AGN at redshift 2–3 approaches that of local normal galaxies. This indicates that many larger galaxies contain black holes and it is likely that the bulk of the black holes was produced before most of the stars in the universe. However, only X‐ray surveys in the harder energy bands, where the maximum of the energy density of the X‐ray background resides, will provide the acid test of this picture.