Sowing black hole seeds: Direct collapse black hole formation with
  realistic Lyman-Werner radiation in cosmological simulations
  We study the birth of supermassive black holes from the direct collapse
process and characterize the sites where these black hole seeds form. In the
pre-reionization epoch, molecular hydrogen (H$_2$) is an efficient coolant,
causing gas to fragment and form Population III stars, but Lyman-Werner
radiation can suppress H$_2$ formation and allow gas to collapse directly into
a massive black hole. The critical flux required to inhibit H$_2$ formation,
$J_{\rm crit}$, is hotly debated, largely due to the uncertainties in the
source radiation spectrum, H$_2$ self-shielding, and collisional dissociation
rates. Here, we test the power of the direct collapse model in a
self-consistent, time-dependant, non-uniform Lyman-Werner radiation field --
the first time such has been done in a cosmological volume -- using an updated
version of the SPH+N-body tree code Gasoline with H$_2$ non-equilibrium
abundance tracking, H$_2$ cooling, and a modern SPH implementation. We vary
$J_{\rm crit} $ from $30$ to $10^3$ in units of $J_{21}$ to study how this
parameter impacts the number of seed black holes and the type of galaxies which
host them. We focus on black hole formation as a function of environment, halo
mass, metallicity, and proximity of the Lyman-Werner source. Massive black hole
seeds form more abundantly with lower $J_{\rm crit}$ thresholds, but regardless
of $J_{\rm crit}$, these seeds typically form in halos that have recently begun
star formation. Our results do not confirm the proposed atomic cooling halo
pair scenario; rather black hole seeds predominantly form in low-metallicity
pockets of halos which already host star formation.
