from clusters, a crucial point will be to conclusively assess the nature of the mechanism responsible for the emission. In the present study, we focus on how to tell apart gamma rays produced by standard, astrophysical mechanisms such as cosmic rays from those resulting from WIMP dark matter annihilation. On general grounds, we expect to have three handles to differentiate the two emission mechanisms:

-   the [*gamma-ray spectrum*]{}: models for cosmic ray production of gamma rays predict a flux as a function of energy which differs from what expected out of dark matter annihilation. The low photon statistics represents a challenge for meaningful discrimination based on the gamma-ray spectrum. We thus study the best angular and energy range, and propose a technique based on hardness ratios that will help to discriminate cosmic rays from dark matter

-   the [*spatial distribution*]{}: depending upon assumptions on the dark matter substructure distribution and density profile, as well as on the primary cosmic ray source distribution, we predict that clusters can appear to be extended gamma-ray sources. We study whether this can be used to differentiate gamma rays emitted by dark matter from those produced by cosmic rays

-   the [*multi-wavelength emission*]{}: comparing the 