Exploring the high-redshift PBH-$\Lambda$CDM Universe: early black hole seeding, the first stars and cosmic radiation backgrounds

TL;DR

This paper investigates a cosmological model where primordial black holes constitute dark matter, influencing early structure formation, star formation, and cosmic radiation backgrounds, with implications for observations by JWST.

Contribution

It introduces a comprehensive model of PBH dark matter affecting early universe evolution, star formation, and cosmic backgrounds, linking PBHs to galaxy and black hole formation.

Findings

PBH dark matter can explain the origins of early black hole seeds.

The model accounts for observed cosmic infrared and X-ray backgrounds.

JWST observations could detect signatures of high-redshift PBH populations.

Abstract

We explore the observational implications of a model in which primordial black holes (PBHs) with a broad birth mass function ranging in mass from a fraction of a solar mass to $\sim$10$^6$ M$_{\odot}$, consistent with current observational limits, constitute the dark matter component in the Universe. The formation and evolution of dark matter and baryonic matter in this PBH-\LambdaCDM~Universe are presented. In this picture, PBH DM mini-halos collapse earlier than in standard \LambdaCDM, baryons cool to form stars at $z\sim15-20$, and growing PBHs at these early epochs start to accrete through Bondi capture. The volume emissivity of these sources peaks at $z\sim20$ and rapidly fades at lower redshifts. As a consequence, PBH DM could also provide a channel to make early black hole seeds and naturally account for the origin of an underlying dark matter halo - host galaxy and central black hole connection that manifests as the $M_{\rm bh}-\sigma$ correlation. To estimate the luminosity function and contribution to integrated emission power spectrum from these high-redshift PBH DM halos, we develop a Halo Occupation Distribution (HOD) model. In addition to tracing the star formation and reionizaton history, it permits us to evaluate the Cosmic Infrared and X-ray Backgrounds (CIB and CXB). We find that accretion onto PBHs/AGN successfully accounts for the detected backgrounds and their cross-correlation, with the inclusion of an additional IR stellar emission component. Detection of the deep IR source count distribution by the JWST could reveal the existence of this population of high-redshift star-forming and accreting PBH DM.