CMB constraints on primordial black hole dark matter

TL;DR

This paper reevaluates constraints on primordial black hole dark matter using CMB data, finding that previous limits are weaker and more uncertain than previously thought, especially for black holes over 5 solar masses.

Contribution

It provides a revised analysis of CMB constraints on primordial black holes, highlighting uncertainties in accretion modeling and updating previous bounds.

Findings

Planck CMB anisotropy data disfavor black holes >5 solar masses as dark matter

Spectral distortion limits from COBE/FIRAS are not constraining

Previous literature overestimated constraints based on these observables

Abstract

We revisit cosmic microwave background (CMB) constraints on primordial black hole dark matter. Spectral distortion limits from COBE/FIRAS do not impose a relevant constraint. Planck CMB anisotropy power spectra imply that primordial black holes with $m_{BH}\gtrsim 5~M_{\odot}$ are disfavored. However, this is susceptible to sizeable uncertainties due to the treatment of the black hole accretion process. These constraints are weaker than those quoted in earlier literature for the same observables.