Dark matter annihilation and the Galactic Centre Excess

Abstract

We compare the surface brightness profile and morphology of the Galactic Centre Excess (GCE) identified in wide-angle $\gamma$-ray maps from the Fermi-Large Area Telescope to dark matter annihilation predictions derived from high-resolution $\Lambda$CDM magnetohydrodynamic simulations of galaxy formation. These simulations produce isolated, disc-dominated galaxies with structure, stellar populations, gas content, and stellar and halo masses comparable to those of the Milky Way. For a specific choice of annihilation cross-section, they agree well with the Fermi-LAT data over the full observed angular range, $1^{\circ }$ to $15^{\circ }$, whereas their dark-matter only counterparts, lacking any compression of the inner halo by the gravitational effects of the baryons, fail to predict emission as centrally concentrated as observed. These results provide additional support to the hypothesis that the GCE is produced by annihilating dark matter. If, however, it is produced by a different mechanism, they imply a strong upper limit on annihilation rates which can be translated into upper limits on the expected $\gamma$-ray flux not only from the inner Galaxy but also from any substructure, with or without stars, in the Galactic halo.

Accepted to MNRAS letters following minor revision

References in corpus (9)

• The Auriga Project: the properties and formation mechanisms of disc galaxies across cosmic time
• Searching for Dark Matter Annihilation in Recently Discovered Milky Way Satellites with Fermi-LAT
• Baryon effects on the internal structure of LCDM halos in the EAGLE simulations
• A blueprint for detecting supersymmetric dark matter in the Galactic halo
• Constraints on the Galactic Halo Dark Matter from Fermi-LAT Diffuse Measurements
• Precise constraints on the dark matter content of Milky Way dwarf galaxies for gamma-ray experiments
• Origin of chemically distinct discs in the Auriga cosmological simulations
• Properties of HI discs in the Auriga cosmological simulations
• Baryonic effects on the detectability of annihilation radiation from dark matter subhaloes around the Milky Way