High energy gamma-ray constraints on decaying Dark Matter

TL;DR

This paper establishes stringent gamma-ray based constraints on decaying dark matter, significantly limiting its possible decay rates and challenging some interpretations of cosmic ray features, while discussing future observational prospects.

Contribution

It provides new gamma-ray bounds on decaying dark matter from Fermi and H.E.S.S., improving existing limits and evaluating future CTA capabilities.

Findings

Gamma-ray data exclude dark matter decay half-lives up to 10^26-10^27 seconds.

Constraints challenge dark matter explanations for cosmic ray electron/positron features.

Future CTA observations could surpass current gamma-ray bounds.

Abstract

New bounds on decaying Dark Matter are derived from the gamma-ray measurements of (i) the isotropic residual (extragalactic) background by Fermi and (ii) the Fornax galaxy cluster by H.E.S.S. We find that those from (i) are among the most stringent constraints currently available, for a large range of dark matter masses and a variety of decay modes, excluding half-lives up to about 10^26 to few 10^27 seconds. In particular, they rule out the interpretation in terms of decaying dark matter of the e+/- spectral features in PAMELA, Fermi and H.E.S.S., unless very conservative choices are adopted. We also discuss future prospects for CTA bounds from Fornax which, contrary to the present H.E.S.S. constraints of (ii), may allow for an interesting improvement and may become better than those from the current or future extragalactic Fermi data.