Testing stochastic gravitational wave signals from primordial black holes with optical telescopes

Primordial black holes (PBHs) can constitute the predominant fraction of dark matter (DM) if PBHs reside in the currently unconstrained sublunar mass range. PBHs originating from scalar perturbations generated during inflation can naturally appear with a broad spectrum in a class of models. The resulting stochastic gravitational wave (GW) background generated from such PBH production can account for the recently reported North American Nanohertz Observatory for Gravitational Waves (NANOGrav) pulsar timing array data signal, and will be testable in future GW observations by interferometer-type experiments such as Laser Interferometer Space Antenna (LISA). We show that the broad mass function of such PBH DM is already being probed by Subaru Hyper Suprime-Cam (HSC) microlensing data and is consistent with a detected candidate event. Upcoming observations of HSC will be able to provide an independent definitive test of the stochastic GW signals originating from such PBH DM production scenarios. (C) 2021 The Authors. Published by Elsevier B.V.

Automated summary

This study suggests that primordial black holes can be a major component of dark matter, originating from scalar perturbations during inflation which may produce a broad spectrum gravitational wave background. These gravitational wave signals, consistent with NANOGrav pulsar timing array data, can be tested in future GW observations using interferometer-type experiments like LISA. Microlensing data from HSC has already probed the broad mass function of PBH DM, providing an independent test for stochastic GW signals originating from PBH DM production scenarios in the future.