Dark Matter decay and annihilation in the Local Universe: CLUES from
  Fermi
  We present all-sky simulated Fermi maps of gamma-rays from dark matter decay
and annihilation in the Local Universe. The dark matter distribution is
obtained from a constrained cosmological simulation of the neighboring
large-scale structure provided by the CLUES project. The dark matter fields of
density and density squared are then taken as an input for the Fermi
observation simulation tool to predict the gamma-ray photon counts that Fermi
would detect in 5 years of all-sky survey for given dark matter models.
Signal-to-noise sky maps have also been obtained by adopting the current
Galactic and isotropic diffuse background models released by the Fermi
collaboration. We point out the possibility for Fermi to detect a dark matter
gamma-ray signal in local extragalactic structures. In particular, we conclude
here that Fermi observations of nearby clusters (e.g. Virgo and Coma) and
filaments are expected to give stronger constraints on decaying dark matter
compared to previous studies. As an example, we find a significant
signal-to-noise ratio in dark matter models with a decay rate fitting the
positron excess as measured by PAMELA. This is the first time that dark matter
filaments are shown to be promising targets for indirect detection of dark
matter. On the other hand, the prospects for detectability of annihilating dark
matter in local extragalactic structures are less optimistic even with extreme
cross-sections. We make the dark matter density and density squared maps
available online at http://www.clues-project.org/articles/darkmattermaps.html
