Population III star formation near high-redshift active galactic nuclei

TL;DR

This study uses cosmological simulations to explore how early supermassive black holes influence Population III star formation, revealing conditions that delay collapse and promote large star clusters or black holes, with potential JWST detectability.

Contribution

It models the impact of accreting SMBHs on nearby dark-matter haloes, showing how radiation delays collapse and affects Population III star formation in the early universe.

Findings

SMBH radiation can delay gravitational collapse in nearby haloes.

Elevated free-electron fraction stimulates H2 formation, aiding cooling.

Pop III clusters could be detectable by JWST at high redshifts.

Abstract

Using cosmological radiation-hydrodynamical simulations, we study the effect of accreting supermassive black holes (SMBHs) on nearby dark-matter (DM) haloes in the very early universe. We find that an SMBH with a spectral energy distribution (SED) extending from the near-ultraviolet to hard X-rays, can produce a radiation background sufficient to delay gravitational collapse in surrounding DM haloes until up to $10^7$ M$_\odot$ of zero-metallicity gas is available for the formation of Population III (Pop III) stars or direct-collapse black holes (DCBHs). We model three scenarios, corresponding to an SMBH located at physical distances of 10, 100, and 1000 kpc from the Pop III host DM halo. Using these three scenarios, we use the SED to compute self-consistent photoionization, photoheating, and photodissociation rates. We include the effects of Compton scattering and gas self-shielding. The X-ray portion of the spectrum maintains an elevated free-electron fraction as the gas collapses to high density. This stimulates H2 formation, allowing the gas to cool further while counteracting the dissociation of H2 by Lyman-Werner radiation. As a result, a large cluster of Pop III stars is expected to form, except in the case with the most intense radiation in which a DCBH may instead form. Our simulated Pop III clusters have comparable HeII 1640 luminosities to the recently discovered Pop III host candidate near GN-z11, observed by the James Webb Space Telescope. In two of the scenarios we consider, the resulting clusters could be detectable using the telescope's NIRSpec instrument out to z ~ 15.