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General Relativity and Quantum Cosmology, gr-qc,Astrophysics, Cosmology and Extragalactic Astrophysics, astro-ph.CO
Abstract:
A significant fraction of cosmological dark matter can be formed by very
dense macroscopic objects, for example primordial black holes. Gravitational
waves offer a promising way to probe of these kinds of dark matter candidates,
in a parameter space region that is relatively untested by electromagnetic
observations. In this work we consider an ensemble of macroscopic dark matter
with masses in the range $10^{-13}$ - $10^{3}\,M_{\odot}$ orbiting a
super-massive black hole. While the strain produced by an individual dark
matter particle will be very small, gravitational waves emitted by a large
number of such objects will add incoherently and produce a stochastic
gravitational-wave background. We show that LISA can be a formidable machine
for detecting the stochastic background of such objects orbiting the black hole
in the center of the Milky Way, Sgr$\mspace{2mu}$A$^{\!*}$, if a dark matter
spike of the type originally predicted by Gondolo and Silk forms near the
central black hole.
