Feedback-regulated Super Massive Black Hole Seed Formation

TL;DR

This paper investigates the formation conditions and abundance of direct collapse black holes as seeds for supermassive black holes, emphasizing the roles of UV radiation, galactic winds, and cosmic evolution.

Contribution

It provides a comprehensive model for DCBH formation, incorporating local UV flux variations, galactic outflows, and pollution, and estimates their abundance over cosmic time.

Findings

DCBH abundance increases from z=20 to z=10.

Galactic winds can suppress DCBH formation by several orders of magnitude.

DCBH formation is more likely around UV-bright star-forming galaxies.

Abstract

The nature of the seeds of high-redshift supermassive black holes (SMBHs) is a key question in cosmology. Direct collapse black holes (DCBH) that form in pristine, atomic-line cooling halos, illuminated by a Lyman-Werner (LW) UV flux exceeding a critical threshold J_crit, represent an attractive possibility. We investigate when and where these conditions are met during cosmic evolution. For the LW intensity, J_LW, we account for departures from the background value in close proximity to star forming galaxies. For the pristine halo fraction, we account for both (i) supernova driven outflows, and (ii) the inherent pollution from progenitor halos. We estimate the abundance of DCBH formation sites, n_DCBH(z), and find that it increases with cosmic time from n_DCBH(z=20) ~ 1e-12 -1e-7 cMpc^-3 to n_DCBH(z=10) ~ 1e-10 - 1e-5 cMpc^-3. Our analysis shows the possible importance of galactic winds, which can suppress the predicted n_DCBH by several orders of magnitude, and cause DCBH formation to preferentially occur around the UV-brightest (M_UV ~ -22 to -20) star forming galaxies. Our analysis further highlights the dependence of these predictions on (i) the escape fraction of LW photons, (ii) J_crit, and (iii) the galactic outflow prescription.