CMB bounds on primordial black holes with dark matter mini-halos: the role of radiative feedback

TL;DR

This paper revisits cosmic microwave background constraints on primordial black holes, highlighting that including dark matter mini-halos significantly relaxes these bounds due to reduced accretion effects.

Contribution

It demonstrates that previous constraints overestimated the impact of dark matter mini-halos on black hole accretion and CMB bounds.

Findings

Constraints for naked black holes remain similar.

Dark matter mini-halos drastically relax bounds.

Mini-halos may not boost accretion as previously thought.

Abstract

Observations of the cosmic microwave background constrain the abundance of primordial black holes, as these would accrete gas and inject energy into the cosmological medium. We have revisited these constraints, taking into account the local heating and ionisation of the gas around the black holes. While constraints for \textit{naked} black holes are not significantly affected, bounds including dark matter mini-halos are drastically relaxed. This result suggests that previous analysis may have significantly overestimated the role of dark matter mini-halos in boosting the accretion rates.