Precursor active galaxies and the cosmic X-ray background

The suggestion that most of the cosmic X-ray background arises from thermal X-ray emission associated with black hole accretion disks for compact objects formed before galaxies is examined. The authors favour a model where the onset of significant X-rays takes place within the epoch of galaxy formation when accretion disks are created by the interaction between massive black holes of pregalactic origin and young galaxies. (author)