Tidal effects of dark matter halo around a galactic black hole

TL;DR

This paper explores how dark matter halos influence tidal forces and geodesic deviations around galactic black holes, revealing dependencies on dark matter mass and galaxy scale that differ from standard black hole models.

Contribution

It provides a novel analysis of tidal effects in black hole spacetimes influenced by dark matter halos, highlighting the impact of dark matter properties on tidal forces and geodesic deviation.

Findings

Tidal forces depend on dark matter halo mass and galaxy scale.

Angular tidal force increases monotonically with dark matter mass.

Dark matter effects are more pronounced for high-energy test particles.

Abstract

We have investigated the tidal forces and geodesic deviation motion in the spacetime of a black hole in the galaxy with dark matter halo. Our results show that the tidal force and geodesic deviation motion depend on the dark matter halo mass and the typical lengthscale of galaxy. The effect of the typical lengthscale of galaxy on tidal force is opposite to that of dark matter mass. For the radial tidal force, with the increasing mass of dark matter, it increases in the region far from the black hole, but decreases in the region near black hole. For the angular tidal force, its absolute value of angular tidal force monotonously increases with the dark matter halo mass. Especially, the angular tidal force also depends on the particle's energy and the effects of dark matter become more distinct for the test particle with high energy, which is different from those in the usual static black hole spacetimes. We also present the change of geodesic deviation vector with the dark matter halo mass and the typical lengthscale of galaxy under two kinds of initial conditions.