The Emergence and Ionizing Feedback of Pop III.1 Stars as Progenitors for Supermassive Black Holes

TL;DR

This study uses advanced simulations to explore how Population III.1 stars could have formed supermassive black holes in the early universe, matching observed black hole densities.

Contribution

It provides the first detailed radiation-hydrodynamics simulations of Pop III.1 stars' feedback and estimates their role in early SMBH formation, aligning with observational data.

Findings

Pop III.1 stars produce large ionized regions extending into the intergalactic medium.

The ionization flux influences the size of HII regions, while formation environment affects redshift.

Estimated SMBH density from Pop III.1 progenitors matches observational constraints.

Abstract

Recent observations by JWST reveal an unexpectedly abundant population of rapidly growing supermassive black holes (SMBHs) in the early Universe, underscoring the need for improved models for their origin and growth. Employing new full radiative transfer hydrodynamical simulations of galaxy formation, we investigate the local and intergalactic feedback of SMBH progenitors for the Population III.1 scenario, i.e., efficient formation of supermassive stars from pristine, undisturbed dark matter minihalos. Our cosmological simulations capture the R-type expansion phase of these Pop III.1 stars, with their H-ionizing photon luminosities of $\sim10^{53}\,{\rm s}^{-1}$ generating HII regions that extend deep into the intergalactic medium, reaching comoving radii of $r_{\rm HII}\sim 1\,{\rm cMpc}$. We vary both the Pop III.1 ionization flux and cosmological formation environments, finding the former regulates their final $r_{\rm HII}$, whereas the latter is more important in setting their formation redshift. We use the results from our radiation-hydrodynamics simulations to estimate the cosmic number density of SMBHs, $n_{\rm SMBH}$, expected from Pop III.1 progenitors. We find $n_{\rm SMBH}\sim10^{-1}\,{\rm cMpc}^{-3}$, consistent with the results inferred from recent observations of the local and high redshift universe. Overall, this establishes Pop III.1 progenitors as viable candidates for the formation of the first SMBHs, and emphasises the importance of exploring heavy mass seed scenarios.