A constraint on light primordial black holes from the interstellar medium temperature

TL;DR

This paper uses the temperature of the interstellar medium in dwarf galaxy Leo T to place new constraints on the abundance of light primordial black holes as dark matter candidates, based on their Hawking radiation effects.

Contribution

It introduces a novel astrophysical constraint on light primordial black holes using interstellar medium temperature measurements.

Findings

Bounds are competitive for black holes with mass less than 5×10^{-17} solar masses.

Primordial black holes could significantly heat the interstellar medium through Hawking radiation.

New constraints surpass previous limits for certain light black hole masses.

Abstract

Primordial black holes are a viable dark matter candidate. They decay via Hawking evaporation. Energetic particles from the Hawking radiation interact with interstellar gas, depositing their energy as heat and ionization. For a sufficiently high Hawking temperature, fast electrons produced by black holes deposit a substantial fraction of energy as heat through the Coulomb interaction. Using the dwarf galaxy Leo T, we place an upper bound on the fraction of primordial black hole dark matter. For $M < 5 \times 10^{-17} M_\odot$, our bound is competitive with or stronger than other bounds.