The effects of metallicity and cooling physics on fragmentation:
  implications on direct-collapse black hole formation
  A promising supermassive black hole seed formation channel is that of direct
collapse from primordial gas clouds. We perform a suite of 3D hydrodynamics
simulations of an isolated turbulent gas cloud to investigate conditions
conducive to forming massive black hole seeds via direct collapse, probing the
impact of cloud metallicity, gas temperature floor and cooling physics on cloud
fragmentation. We find there is no threshold in metallicity which produces a
sharp drop in fragmentation. When molecular cooling is not present, metallicity
has little effect on fragmentation. When molecular cooling is present,
fragmentation is suppressed by at most $\sim 25\%$, with the greatest
suppression seen at metallicities below $2\%$ solar. A gas temperature floor
$\sim 10^{4}$K produces the largest drop in fragmentation of any parameter
choice, reducing fragmentation by $\sim 60\%$. At metallicities below $2\%$
solar or at temperatures $\sim 10^{3}$K we see a reduction in fragmentation
$\sim 20-25 \%$. For a cloud of metallicity $2\%$ solar above and a temperature
below $10^3$K, the detailed choices of temperature floor, metallicity, and
cooling physics have little impact on fragmentation.
