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

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 $f_{\mathrm{PBH}}=1$ over the mass range $10^{-14}{M}_{\odot }\lesssim m_{\mathrm{PBH}}\lesssim 10^{-8}{M}_{\odot }$. Our results show that the Galactic Center could appear as a GW-bright source, enabling new insights into dark matter and its distribution.

7 pages, 2 figures