Observational Consequences of Hawking Radiation from Primordial Black Holes

Black holes that were formed in the early universe, known as primordial black holes, are promising candidates for dark matter. They evaporate in a process known as Hawking radiation, the rate of which is dependant of the black holes' mass and leads to observable effects on the universe around them. These effects can be especially impactful during the minutes after the Big Bang for light PBHs, and near the center of the Milky Way for black holes evaporating today. The existence and evaporation of PBHs in the very early universe could affect the light element abundances that are measured today. We utilize modern measurements of the light element abundances to update the constraints on PBHs from Big Bang nucleosynthesis. Additionally, we use our own black hole model and template analysis to show that PBHs can explain the excess of 511 keV photons originating from the center of the Milky Way. Finally, we assess the ability of future gamma ray telescopes to detect Hawking radiation from PBHs emanating from the Inner Galaxy. We find that these telescopes will be able to precisely measure the abundance and mass distribution of PBHs, if they exist, within a mass range of m_BH ~ (0.6-20) * 10^16 g if the black holes make up one part in 10^6-10^7 of the total dark matter. These constraints will improve upon current constraints by at least two orders of magnitude.