Gamma-ray sensitivity to dark matter subhalo modelling at high latitudes
  Searches for "dark" subhaloes in gamma-ray point-like source catalogues are
among promising strategies for indirect dark matter detection. Such a search is
nevertheless affected by uncertainties related, on the one hand, to the
modelling of the dark matter subhalo distribution in Milky-Way-like galaxies,
and, on the other hand, to the sensitivity of gamma-ray instruments to the dark
matter subhalo signals. In the present work, we assess the detectability of
dark matter subhaloes in Fermi-LAT catalogues, taking into accounts
uncertainties associated with the modelling of the Galactic subhalo population.
We use four different halo models bracketing a large set of uncertainties. For
each model, adopting an accurate detection threshold of the LAT to dark matter
subhalo signals and comparing model predictions with the number of unassociated
point-sources in Fermi-LAT catalogues, we derive upper limits on the
annihilation cross section as a function of dark matter mass. Our results show
that, even in the best-case scenario (i.e. DMonly subhalo model), which does
not include tidal disruption from baryons, the limits on the dark matter
parameter space are less stringent than current gamma-ray limits from dwarf
spheroidal galaxies. Comparing the results obtained with the different subhalo
models, we find that baryonic effects on the subhalo population are significant
and lead to dark matter constraints that are less stringent by a factor of
about 2 to 5. This uncertainty comes from the unknown resilience of dark matter
subhaloes to tidal disruption.
