Updated cosmic-ray and radio constraints on light dark matter: Implications for the GeV gamma-ray excess at the Galactic center

TL;DR

This paper updates constraints on light dark matter explanations for the Galactic center gamma-ray excess, showing that cosmic-ray and radio data strongly challenge the dark matter interpretation, especially for leptonic channels.

Contribution

It provides the latest indirect detection bounds, including improved cosmic-ray antiproton limits and radio constraints, specifically tailored to the gamma-ray excess signal.

Findings

Cosmic-ray positron data exclude light leptonic dark matter.

Antiproton limits challenge quark final states in dark matter models.

Radio observations severely constrain leptonic dark matter explanations.

Abstract

The apparent gamma-ray excess in the Galactic center region and inner Galaxy has attracted considerable interest, notably because both its spectrum and radial distribution are consistent with an interpretation in terms of annihilating dark matter particles with a mass of about 10-40 GeV. We confront such an interpretation with an updated compilation of various indirect dark matter detection bounds, which we adapt to the specific form required by the observed signal. We find that cosmic-ray positron data strongly rule out dark matter annihilating to light leptons, or 'democratically' to all leptons, as an explanation of the signal. Cosmic-ray antiprotons, for which we present independent and significantly improved limits with respect to previous estimates, are already in considerable tension with DM annihilation to any combination of quark final states; the first set of AMS-02 data will thus be able to rule out or confirm the DM hypothesis with high confidence. For reasonable assumptions about the magnetic field in the Galactic center region, radio observations independently put very severe constraints on a DM interpretation of the excess, in particular for all leptonic annihilation channels.