Effect of Primordial Black Holes on the global 21-cm signal

TL;DR

This paper explores how primordial black holes, as seeds for early AGNs, could significantly influence the evolution of the 21-cm global signal, challenging the star-formation-only models of the early universe.

Contribution

It introduces an analytical model linking primordial black holes to early AGNs and demonstrates their potential impact on the 21-cm signal evolution.

Findings

Primordial black holes can significantly alter the 21-cm signal evolution.

Early AGNs seeded by PBHs may explain recent JWST observations.

PBHs influence the timing and features of the 21-cm global signal.

Abstract

The 21-cm global signal, a treasure trove of information about the nature of the first luminous sources of the Universe, has traditionally been modelled assuming that these early sources were predominantly star-forming galaxies. However, recent observations by the James Webb Space Telescope (JWST) have revealed several AGNs as early as z ~ 10 - 10.4 . In light of this, it is important to investigate the contribution of such AGNs to the 21-cm signal. Assuming that these AGNs are seeded by Primordial Black Holes (PBHs) and employing an analytical PBH model, consistent with existing cosmological and astrophysical constraints, we show that these exotic objects can have a significant impact on the redshift evolution of the global signal.