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Session 100 - Accretion Disks and Black Holes.
Display session, Thursday, January 16
Metropolitan Ballroom,
We present a model of formation of quasar black holes from the collapse of primordial gas clouds. The cosmologically expanding initial gas cloud turns around and collapses at redshift of around 8 eventually to a protogalactic disk with a massive halo, while acquiring angular momentum by tidal torques from nearby protogalaxies. The size and mass of the disk are expressed in terms of the usual cosmological parameters, Ømega_b/Ømega, and the mass of the initial cloud. The subsequent evolution of the disk gas are described by the accretion disk equations with the viscosity provided by magnetic fields from supernovae or other stellar expulsions arising out of an assumed early phase of star formation. The first phase of accretion which occurs in the gravitational potential of the halo is calculated in some detail while the second phase of the core collapse, due to instabilities induced by self-gravity or due to magnetic braking by large scale fields, is treated approximately. For typical values of the parameters involved in the model, a supermassive black hole forms in 10^8 yrs after the initial collapse. This mechanism also provides a simple but plausible explanation of the observed field strength of \mu G in galaxies at redshifts of 2.
