Searching for Primordial Black Holes in the radio and X-ray sky

TL;DR

This study models gas accretion onto primordial black holes in the Milky Way and compares predicted radio and X-ray emissions with observations, strongly constraining their role as dark matter candidates.

Contribution

It provides the first robust constraints on primordial black holes as dark matter using radio and X-ray data, excluding certain mass ranges at high significance.

Findings

Primordial black holes of around 10 solar masses cannot account for all dark matter.

Radio and X-ray observations exclude their contribution at 5σ and 40σ levels.

Future surveys could further identify or constrain such black hole populations.

Abstract

We model the accretion of gas onto a population of massive primordial black holes in the Milky Way, and compare the predicted radio and X-ray emission with observational data. We show that under conservative assumptions on the accretion process, the possibility that ${\cal O}(10) \, M_\odot$ primordial black holes can account for all of the dark matter in the Milky Way is excluded at $5\sigma$ by a comparison with a VLA radio catalog at $1.4$ GHz, and at $\simeq 40\sigma$ by a comparison with a Chandra X-ray catalog ($0.5 - 8$ keV). We argue that this method can be used to identify such a population of primordial black holes with more sensitive future radio and X-ray surveys.