Determination of the Dark Matter profile from the EGRET excess of diffuse Galactic gamma radiation

TL;DR

This paper interprets the EGRET gamma-ray excess as dark matter annihilation, using gamma-ray data to infer the dark matter halo profile and the survival of clumpy substructures within the Milky Way.

Contribution

It provides a method to determine the dark matter halo profile from gamma-ray data and discusses the survival probability of clumpy dark matter structures.

Findings

The diffuse component fits an NFW profile.

The clumpy component is compatible with a cored profile.

Tidal forces reduce the gamma-ray signal from the Galactic center.

Abstract

The excess above 1 GeV in the energy spectrum of the diffuse Galactic gamma radiation, measured with the EGRET experiment, can be interpreted as the annihilation of Dark Matter (DM) particles. The DM is distributed in a halo around the Milky Way. Considering the directionality of the gamma ray flux it is possible to determine the halo profile. The DM within the halo has a smooth and a clumpy component.These components can have different profiles as suggested by N-body simulations and the data is indeed compatible with a NFW profile for the diffuse component and a cored profile for the clumpy component.These DM clumps can be partly destroyed by tidal forces from interactions with stars and the gravitational potential of the Galactic disc.This effect mainly decreases the annihilation signal from the Galactic centre (GC). In this paper constraints on the different profiles and the survival probability of the clumps are discussed.