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Mass without Radiation: The X-ray background and the Black Hole mass density

by Dr. Andrea Comastri (INAF Osservatorio Astronomico di Bologna)

Jun 23, 2014 from 02:30 PM to 04:00 PM

Where IRA meeting room (4th floor, CNR research area, via Gobetti 101)

Contact Name Marcello Giroletti

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A recent analysis of black hole scaling relations, used to estimate the local mass density in black holes, has indicated that their normalization should be increased by approximately a factor of five.  The local black hole mass density is connected to the mean radiative efficiency of accretion through the time integral of the AGN volume density. The ``observed'' increase of the local black holes mass density would have some interesting  consequences.  One possibility is that  most of the Black Hole growth is via radiatively inefficient channels such as super Eddington accretion.  We discuss the possibility that a large population of heavily buried, Compton thick AGN,  could be responsible of the "higher" mass density without violating the  limit imposed by the cosmic backgrounds.

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