Dark matter searches in the gamma-ray extragalactic background via
  cross-correlations with galaxy catalogues
  We compare the measured angular cross-correlation between the Fermi-LAT
gamma-ray sky and catalogues of extra-galactic objects with the expected signal
induced by weakly interacting massive particle (WIMP) dark matter (DM). We
include a detailed description of the contribution of astrophysical gamma-ray
emitters such as blazars, misaligned AGN and star forming galaxies, and perform
a global fit to the measured cross-correlation. Five catalogues are considered:
SDSS-DR6 quasars, 2MASS galaxies, NVSS radio galaxies, SDSS-DR8 Luminous Red
Galaxies and SDSS-DR8 main galaxy sample. To model the cross-correlation signal
we use the halo occupation distribution formalism to estimate the number of
galaxies of a given catalogue in DM halos and their spatial correlation
properties. We discuss uncertainties in the predicted cross-correlation signal
arising from the DM clustering and WIMP microscopic properties, which set the
DM gamma-ray emission. The use of different catalogues probing objects at
different redshifts reduces significantly, though not completely, the
degeneracy among the different gamma-ray components. We find that the presence
of a significant WIMP DM signal is allowed by the data but not significantly
preferred by the fit, although this is mainly due to a degeneracy with the
misaligned AGN component. With modest substructure boost, the sensitivity of
this method excludes thermal annihilation cross sections at 95% C.L. for WIMP
masses up to few tens of GeV. Constraining the low-redshift properties of
astrophysical populations with future data will further improve the sensitivity
to DM.
