PIERO MADAU University of California, Santa Cruz (USA). There is currently little or no consensus on the evolution of massive black holes along the cosmic history of the Universe. The tension between the need of rapid accretion required by the presence of SMBHs already in place at z=7, and the strict limits on the accreted mass derived by observations of the X-ray background, can be eased assuming an early phase of supercritical accretion via radiative inefficient flows.

DATA: 01-10-2012