COLLAPSE OF PRIMORDIAL GAS CLOUDS AND THE FORMATION OF QUASAR BLACK-HOLES

The formation of quasar black holes during the hydrodynamic collapse o f protogalactic gas clouds is discussed. The dissipational collapse an d long-term dynamical evolution of these systems is analyzed using thr ee-dimensional numerical simulations. The calculations focus on the fi nal collapse stages of the inner baryonic component and therefore igno re the presence of dark matter. Two types of initial conditions are co nsidered: uniformly rotating spherical clouds, and irrotational ellips oidal clouds. In both cases the clouds are initially cold, homogeneous , and not far from rotational support (T/\ W \ almost-equal-to 0.1). A lthough the details of the dynamical evolution depend sensitively on t he initial conditions, the qualitative features of the final configura tions do not. Most of the ps is found to fragment into small dense clu mps, that eventually make up a spheroidal component resembling a galac tic bulge. About 5% of the initial mass remains in the form of a smoot h disk of gas supported by rotation in the gravitational potential wel l of the outer spheroid. If a central seed black hole of mass greater than or similar to 10(6) M. forms, it can grow by steady accretion fro m the disk and reach a typical quasar black hole mass approximately 10 (8) M. in less than 5 x 10(8) yr. In the absence of a sufficiently mas sive seed, dynamical instabilities in a strongly self-gravitating inne r region of the disk will inhibit steady accretion of gas and may prev ent the immediate formation of a quasar.