Direct Collapse to Supermassive Black Hole Seeds with Radiation
  Transfer: Cosmological Halos
  We have modeled direct collapse of a primordial gas within dark matter halos
in the presence of radiative transfer, in high-resolution zoom-in simulations
in a cosmological framework, down to the formation of the photosphere and the
central object. Radiative transfer has been implemented in the flux-limited
diffusion (FLD) approximation. Adiabatic models were run for comparison. We
find that (a) the FLD flow forms an irregular central structure and does not
exhibit fragmentation, contrary to adiabatic flow which forms a thick disk,
driving a pair of spiral shocks, subject to Kelvin-Helmholtz shear instability
forming fragments; (b) the growing central core in the FLD flow quickly reaches
~10 Mo and a highly variable luminosity of 10^{38}-10^{39} erg/s, comparable to
the Eddington luminosity. It experiences massive recurrent outflows driven by
radiation force and thermal pressure gradients, which mix with the accretion
flow and transfer the angular momentum outwards; and (c) the interplay between
these processes and a massive accretion, results in photosphere at ~10 AU. We
conclude that in the FLD model (1) the central object exhibits dynamically
insignificant rotation and slower than adiabatic temperature rise with density;
(2) does not experience fragmentation leading to star formation, thus promoting
the fast track formation of a supermassive black hole (SMBH) seed; (3)
inclusion of radiation force leads to outflows, resulting in the mass
accumulation within the central 10^{-3} pc, which is ~100 times larger than
characteristic scale of star formation. The inclusion of radiative transfer
reveals complex early stages of formation and growth of the central structure
in the direct collapse scenario of SMBH seed formation.
