Testing Stochastic Gravitational Wave Signals from Primordial Black Holes with Optical Telescopes

TL;DR

This paper explores how primordial black holes as dark matter could produce a stochastic gravitational wave background detectable by future observatories, and how optical telescopes can test these scenarios through microlensing data.

Contribution

It links primordial black hole dark matter models with gravitational wave signals and demonstrates how optical microlensing data can test these models.

Findings

The stochastic GW background from PBHs can explain NANOGrav data.

Current Subaru HSC microlensing data is consistent with PBH dark matter.

Future HSC observations can definitively test the PBH GW production scenario.

Abstract

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.