High energy gamma-ray constraints on decaying Dark Matter
  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.
