Gravitational Wave Burst from Bremsstrahlung in Milky Way Can Discover Sub-Solar Dark Matter in Near Future

TL;DR

This paper proposes that gravitational wave emissions from hyperbolic encounters of primordial black holes in the Milky Way could reveal the presence of sub-solar mass dark matter, especially if future GW detectors observe signals with high signal-to-noise ratios.

Contribution

It introduces a novel method to detect sub-solar mass primordial black hole dark matter through gravitational bremsstrahlung signals in the Milky Way using upcoming GW observatories.

Findings

Signal-to-noise ratio can exceed five within one year for certain dark matter fractions.

Galactic Center could be identified as a bright gravitational wave source.

Detection is feasible for PBH masses between 10^{-14} and 10^{-8} solar masses.

Abstract

What is Dark Matter, and what is its concentration in the Milky Way remains an open question in physics. We show that if a significant fraction of dark matter is composed of sub-solar mass primordial black holes (PBHs), gravitational bremsstrahlung resulting from hyperbolic encounters between unbound PBHs within the galactic halos can generate distinctive chromatic gravitational-wave (GW) emission concentrated around the galactic dark matter halo, and it provides a direct window to discover such compact objects. We find that for both generalized NFW and Einasto dark matter profiles of Milky Way, the signal-to-noise ratio can be more than five in one year of observation for the upcoming ground based GW observatories Cosmic Explorer if PBH dark matter fraction $f_{\rm PBH} = 1$ over the mass range $10^{-14} M_\odot \lesssim m_{\rm PBH} \lesssim 10^{-8} M_\odot$. Our results show that the Galactic Center could appear as a GW-bright source, enabling new insights into dark matter and its distribution.