Dark matter spikes in the vicinity of Kerr black holes

TL;DR

This paper investigates how the spin of Kerr black holes influences the surrounding dark matter density spikes, revealing that rotation enhances the density near the black hole and could impact indirect dark matter detection efforts.

Contribution

It provides a relativistic analysis of dark matter spikes around spinning black holes using Kerr geometry, highlighting the effect of black hole spin on dark matter density profiles.

Findings

Rotation increases dark matter density near Kerr black holes.

Enhanced density could lead to higher dark matter annihilation signals.

Black hole gravitational effects dominate within the influence radius.

Abstract

The growth of a massive black hole will steepen the cold dark matter density at the center of a galaxy into a dense spike, enhancing the prospects for indirect detection. We study the impact of black hole spin on the density profile using the exact Kerr geometry of the black whole in a fully relativistic adiabatic growth framework. We find that, despite the transfer of angular momentum from the hole to the halo, rotation increases significantly the dark matter density close to the black hole. The gravitational effects are still dominated by the black hole within its influence radius, but the larger dark matter annihilation fluxes might be relevant for indirect detection estimates.