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.

arXiv commentAccepted to MNRAS letters following minor revision

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Cited by in corpus (9)

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• Constraints on dark matter annihilation and decay from the large-scale structure of the nearby universe
• Robust inference of the Galactic centre gamma-ray excess spatial properties
• The effect of stellar encounters on the dark matter annihilation signal from prompt cusps
• Robustness of the Galactic Center Excess Morphology Against Masking
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• Analysis of shape and angular orientation parameters of velocity-dependent dark matter annihilation signals in Galactic Centers for FIRE simulations