The Direct Collapse of Supermassive Black Hole Seeds

The direct collapse model of supermassive black hole seed formation requires that thegas cools predominantly via atomic hydrogen. To this end we simulate the effect of ananisotropic radiation source on the collapse of a halo at high redshift. The radiationsource is placed at a distance of 3 kpc (physical) from the collapsing object and is setto emit monochromatically in the center of the Lyman-Werner (LW) band. The LW radiationemitted from the high redshift source is followed self-consistently using ray tracingtechniques. Due to self-shielding, a small amount of H₂ is able to form at the verycenter of the collapsing halo even under very strong LW radiation. Furthermore, we find thata radiation source, emitting < 10⁵⁴ (~10³ J₂₁) photons per second isrequired to cause the collapse of a clump of M ~ 10⁵ M_⊙. The resultingaccretion rate onto the collapsing object is ~ 0.25 M_⊙ yr^-1.Our results display significant differences, compared to the isotropic radiation field case,in terms of H₂ fraction at an equivalent radius. These differences will significantly effectthe dynamics of the collapse. With the inclusion of a strong anisotropic radiation source, thefinal mass of the collapsing object is found to be M ~ 10⁵ M_⊙. This is consistentwith predictions for the formation of a supermassive star or quasi-star leading to asupermassive black hole.