Relaxing Constraints on Dark Matter Annihilation Near the Supermassive Black Hole in M87

TL;DR

This paper investigates how different assumptions about the dark matter halo profile in M87 affect constraints on dark matter annihilation signals, showing that using a cored profile relaxes these constraints compared to a cuspy profile.

Contribution

It introduces a cored halo model for M87 based on recent kinematic data, demonstrating its impact on dark matter annihilation constraints and highlighting the importance of halo profile assumptions.

Findings

Cored halo models significantly relax annihilation constraints.

Smooth halo component dominates in cored scenarios.

Cuspy models attribute more signal to the density spike.

Abstract

The supermassive black hole at the center of M87 could redistribute dark matter particles within its sphere of influence, creating a high-density region known as a density spike. This spike can significantly enhance dark matter annihilation signals, making M87 a critical target for deriving stringent constraints on annihilation cross sections. In this work, we demonstrate that these constraints are highly sensitive to the choice of the halo density profile for M87. Motivated by recent kinematic studies of M87, we adopt a cored halo model and find that the constraints on dark matter annihilation are significantly relaxed. Specifically, in the cored halo scenario, the smooth part of the halo overwhelmingly dominates the annihilation signals, whereas the commonly-assumed cuspy halo model attributes a major contribution to the spike. We demonstrate this effect using a dark matter model with a light mediator.