Hawking Radiation from non-evaporating primordial black holes cannot enable the formation of direct collapse black holes

TL;DR

This paper investigates whether Hawking radiation from non-evaporating primordial black holes can trigger the formation of supermassive black holes in the early universe, concluding it is unlikely unless PBHs are a major dark matter component and highly clustered.

Contribution

The study establishes constraints on PBH masses and shows Hawking radiation from non-evaporating PBHs cannot facilitate direct collapse black hole formation under typical conditions.

Findings

Hawking radiation from non-evaporating PBHs is insufficient to suppress H2 cooling.

PBHs would need to be a significant dark matter component and clustered to influence SMBH formation.

The effective temperature range of HR from PBHs does not match the critical radiation needed for DCBH formation.

Abstract

The formation of supermassive black holes (SMBHs) in the early Universe is a subject of significant debate. In this study, we examine whether non-evaporating primordial black holes (PBHs) can offer a solution. We establish initial constraints on the range of PBH masses that correspond to Hawking radiation (HR) effective temperatures in the range needed to suppress $H_2$ cooling, which would facilitate the formation of massive black hole seeds in atomic cooling halos. We also investigate the specific intensity of the HR from non-evaporating PBHs and compare it with the critical radiation needed for direct collapse black holes (DCBHs). We show that HR from non-evaporating PBHs cannot serve as an irradiating mechanism to facilitate the formation of the seeds for the SMBHs we observe in the high-redshift Universe unless, perhaps, the PBHs within the relevant mass range comprise a significant fraction of dark matter and are significantly clustered towards the center of the primordial halo.