The Impact of Lyman alpha Trapping on the Formation of Primordial
  Objects
  Numerous cosmological simulations have been performed to study the formation
of the first objects. We present the results of high resolution 3-D
cosmological simulations of primordial objects formation using the adaptive
mesh refinement code FLASH by including in an approximate manner the radiative
transfer effects of Lyman alpha photons. We compare the results of a Lyman
alpha trapping case inside gas clouds with atomic and molecular hydrogen
cooling cases.The principal objective of this research is to follow the
collapse of a zero metallicity halo with an effective equation of state (that
accounts for the trapping) and to explore the fate of a halo in each of the
three cases, specifically, the impact of thermodynamics on fragmentation of
halos.Our results show that in the case of Lyman alpha trapping, fragmentation
is halted and a massive object is formed at the center of a halo. The
temperature of the gas remains well above $10^{4}$ K and the halo is not able
to fragment to stellar masses. In the atomic cooling case, gas collapses into
one or two massive clumps in contrast to the Lyman alpha trapping case. For the
molecular hydrogen cooling case, gas cools efficiently and fragments.The
formation of massive primordial objects is thus strongly dependent on the
thermodynamics of the gas. A salient feature of our results is that for the
formation of massive objects, e.g. intermediate mass black holes, feedback
effects are not required to suppress $H_{2}$ cooling, as molecular hydrogen is
collisionally dissociated at temperatures higher than $10^{4}$ K as a
consequence of Lyman alpha trapping.
