Formation of Super-massive Black Holes
  We show that the rapid formation of super-massive black holes in quasars can indeed be understood in terms of major galaxy mergers followed by disk accretion. The necessary short disk evolution time can be achieved provided the disk viscosity is sufficiently large, which, for instance, is the case for hydrodynamic turbulence, unlimited by shock dissipation. We present numerical calculations for a representative case. This general picture can account for (a) the presence of highly luminous quasars at redshifts z > 6; (b) for the peak in quasar activity at z ~ 2; and (c) for a subsequent rapid disappearance of quasars at later epochs. 
Wolfgang J. Duschl (1), Peter A. Strittmatter (2) ((1) ITA,   Heidelberg, Germany, (2) Steward Observatory, Tucson, AZ, USA)