Simulations of the Birth and Early Growth of Supermassive Black Holes

Our work uses cosmological simulations to study the formation and early growth of direct collapse black holes. In the pre-reionization epoch, molecular hydrogen (H$_{\mathrm{2}})$ causes gas to fragment and form Population III stars, but Lyman-Werner radiation can suppress H$_{\mathrm{2}}$~formation and allow gas to collapse directly into a massive black hole. The critical flux required to inhibit H$_{\mathrm{2~}}$formation, J$_{\mathrm{crit}}$, is hotly debated, largely due to the uncertainties in the source radiation spectrum, H$_{\mathrm{2~}}$self-shielding, and collisional dissociation rates. Here, we test the power of the direct collapse model in a non-uniform Lyman-Werner radiation field, using an updated version of the SPH$+$N-body tree code Gasoline with H$_{\mathrm{2}}$~non-equilibrium abundance tracking, H$_{\mathrm{2}}$cooling, and a modern SPH implementation. We vary J$_{\mathrm{crit~}}$from 30 to 10$^{\mathrm{4}}$~J$_{\mathrm{21~}}$to study the effect on seed black holes, focusing on black hole formation as a function of environment, halo mass, metallicity, and proximity of the Lyman-Werner source. We discuss the constraints on massive black hole occupation fraction in the quasar epoch, and implications for gravitational wave astronomy.