COSMOLOGICAL FORMATION OF QUASAR BLACK-HOLES

Massive black holes (greater than or similar to 10(5) M.) can form in a quasi-spherical collapse of gas clouds, out of nonlinear density perturbations above the Jeans mass after the cosmological recombination [200 less-than-or-similar-to (1 + z) less than or similar to 1400]. Angular momentum and energy are extracted efficiently from the electrons through Compton friction with the cosmic background radiation. Due to the radial Compton drag, the dark-matter mass enclosed within a baryonic shell changes as a function of time. Most of the collapse time is spent near turnaround at low gas densities. During that phase, the cloud can be reionized by a sub-Eddington internal luminosity. The resulting Compton drag eliminates efficiently the angular momentum given to the ionized plasma by tidal gravitational torques. The existence of dust can strongly enhance the coupling of the gas to the radiation. After the cloud collapses by a few orders of magnitude in radius, the photons become trapped and transport angular momentum only locally through radiative viscosity. The reduced centrifugal barrier of the cloud allows it to collapse quasi-spherically down to its Schwarzchild scale. A black hole is produced, surrounded by a dark-matter halo. Later, additional mass accretes into the system, out of which stars can form in orbit around the central black hole.