Investigating the detection of dark matter subhalos as extended sources
  with Fermi-LAT
  Cold dark matter (DM) models for structure formation predict that DM subhalos
are present in the Galaxy. In the standard paradigm of DM as weakly interacting
massive particle, subhalos are expected to shine in gamma rays and to provide a
signal detectable with current instruments, notably with the Large Area
Telescope (LAT) aboard the Fermi~satellite. This is the main motivation behind
searches for DM signals towards dwarf spheroidal galaxies and unidentified
Fermi-LAT sources. A significant angular extension detected from unassociated
sources located at relatively high latitudes is considered a "smoking gun"
signature for identifying DM subhalos. In the present work, we systematically
explore, by means of state-of-the-art models of cold DM halos in the Galaxy,
the detectability of extended subhalos with Fermi-LAT. We simulate a DM signal
exploring different assumptions of subhalos distribution in the Galaxy and DM
profile, and reconstruct its flux through a realistic Fermi-LAT analysis
pipeline. In the most optimistic case, we show that a detection of extended DM
subhalos can be made for annihilation cross sections higher than $3 \times
10^{-26}$ cm$^3$/s (for a 100 GeV DM mass), still compatible with existing
gamma-ray constraints, and that, in this case, the preference for extension of
the source (vs point-like hypothesis) is significant. For fainter signals,
instead, halos not only do not show significant extension, but they are not
even detectable significantly as point-like sources.
