Supermassive black holes surrounded by dark matter modeled as anisotropic fluid: epicyclic oscillations and their fitting to observed QPOs

Abstract

Recently introduced exact solution of the Einstein gravity coupled minimally to an anisotropic fluid representing dark matter can well represent supermassive black holes in galactic nuclei with realistic distribution of dark matter around the black hole, given by the Hernquist-like density distribution. For these fluid-hairy black hole spacetimes, properties of the gravitational radiation, quasinormal ringing, and optical phenomena were studied, giving interesting results. Here, using the range of physical parameters of these spacetimes allowing for their relevance in astrophysics, we study the epicyclic oscillatory motion of test particles in these spacetimes. The frequencies of the orbital and epicyclic motion are applied in the epicyclic resonance variant of the geodesic model of quasiperiodic oscillations (QPOs) observed in active galactic nuclei to demonstrate the possibility to solve the cases where the standard vacuum black hole spacetimes are not allowing for explanation of the observed data. We demonstrate that the geodesic model can explain the QPOs observed in most of the active galactic nuclei for the fluid-hairy black holes with reasonable halo parameters.

Tidal effects of a dark matter halo around a galactic black hole*

“…Recently, Cardoso et al [18] obtained an interesting static black hole solution by solving Einstein's equations with the energy momentum tensor originating from galactic matter, which describes a galactic black hole immersed in a dark matter halo with a Hernquist distribution. With this solution, the effects of a dark mater halo on quasinormal modes, scattering, and optical phenomena have been studied in [19][20][21][22][23][24]. The galactic black hole solution for a black hole surrounded by a dark matter halo with different distributions has been discussed in [25].…”