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