Extreme mass ratio inspirals in the cold vector dark matter environment

Abstract

With regard to the observed dark matter density profiles in galaxies and clusters, the scalar dark matter scenario has been previously studied for its potential detectability through gravitational wave observations at measurable signal-to-noise ratios. In the present study, we consider dark matter described by a massive vector field, also referred to as a Proca field. The density profile in the vicinity of the black hole is explicitly constructed for a broad range of dark matter masses, μ ∼ 10-10-10-15 eV, allowing the dark matter to exhibit both particle and wave-like characteristics. While the computation of the DM density distribution is analytically tractable in the particle regime, we find it convenient to compute the same numerically in the wave regime. Nevertheless, in the outer region, the surrounding dark matter is assumed to follow a broken power-law distribution, represented by a Navarro-Frenk-White (NFW) profile with a central spike. To investigate the detectability of the vector dark matter in the gravitational wave spectrum, we have modelled a stellar-mass black hole (1M⊙) inspiralling into a Schwarzschild black hole of mass 104M⊙ within such a vector dark matter environment. Using this setup, we have analyzed the dephasing in the gravitational wave strain induced by vector dark matter and performed a Fisher forecast for upcoming LISA observations, with particular emphasis on the distinctive features arising in both the particle and wave regimes of the dark matter. Additionally, most of the important results have been compared with the scalar dark matter case.