Planck Constraint on Relic Primordial Black Holes

TL;DR

This paper uses CMB and gamma-ray data to set new limits on primordial black holes in the 10^{15}-10^{17} g mass range, ruling out their dominance as dark matter in this window.

Contribution

It provides the strongest constraints to date on PBH abundance in the specified mass range by combining Planck CMB data and gamma-ray background observations.

Findings

CMB data constrains PBHs around 10^{15}-10^{16} g.

Gamma-ray background constrains PBHs above 10^{16} g.

PBHs are ruled out as dominant dark matter in the 10^{16}-10^{17} g range.

Abstract

We investigate constraints on the abundance of primordial black holes (PBHs) in the mass range 10^{15}-10^{17} g using data from the Cosmic Microwave Background (CMB) and MeV extragalactic gamma-ray background (EGB). Hawking radiation from PBHs with lifetime greater than the age of the universe leaves an imprint on the CMB through modification of the ionization history and the damping of CMB anisotropies. Using a model for redshift dependent energy injection efficiencies, we show that a combination of temperature and polarization data from Planck provides the strongest constraint on the abundance of PBHs for masses \sim 10^{15}-10^{16} g, while the EGB dominates for masses \gtrsim 10^{16} g. Both the CMB and EGB now rule out PBHs as the dominant component of dark matter for masses \sim 10^{16}-10^{17} g. Planned MeV gamma-ray observatories are ideal for further improving constraints on PBHs in this mass range.