Electromagnetic probes of primordial black holes as dark matter

Understand

The LIGO discoveries have rekindled suggestions that primordial black holes (BHs) may constitute part to all of the dark matter (DM) in the Universe.

• Such suggestions came from 1) the observed merger rate of the BHs, 2) their unusual masses, 3) their low/zero spins, and 4) also from the independently uncovered cosmic infrared background (CIB) fluctuations signal of high amplitude and coherence with unresolved cosmic X-ray background (CXB).
• Here we summarize the prospects to resolve this important issue with electromagnetic observations using the instruments and tools expected in the 2020's.
• These prospects appear promising to make significant, and potentially critical, advances.