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Abstract 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 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, nonuniform Lyman–Werner radiation field—the first time such has been done in a cosmological volume—using an updated version of the Smooth Particle Hydrodynamics (SPH)+ N -body tree code Gasoline with H 2 nonequilibrium abundance tracking, H 2 cooling, and a modern SPH implementation. We vary J 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 that 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 crit thresholds, but regardless of J 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 that already host star formation.
Dunn et al. (Fri,) studied this question.