The 511 keV Excess and Primordial Black Holes

Understand

An excess of 511 keV photons has been detected from the central region of the Milky Way.

• It has been suggested that the positrons responsible for this signal could be produced through the Hawking evaporation of primordial black holes.
• After evaluating the constraints from INTEGRAL, COMPTEL, and Voyager 1, we find that black holes in mass range of $\sim(1-4)\times10^{16}$ g could potentially produce this signal if they make up a small fraction of the total dark matter density.
• Proposed MeV-scale gamma-ray telescopes such as AMEGO or e-ASTROGAM should be able to test this class of scenarios by measuring the diffuse gamma ray emission from the Milky Way's inner halo.