Dark Matter search in dwarf irregular galaxies with the Fermi Large Area
  Telescope
  We analyze 11 years of Fermi-LAT data corresponding to the sky regions of 7
dwarf irregular (dIrr) galaxies. DIrrs are dark matter (DM) dominated systems,
proposed as interesting targets for the indirect search of DM with gamma rays.
The galaxies represent interesting cases with a strong disagreement between the
density profiles (core vs. cusp) inferred from observations and numerical
simulations. In this work, we addressed the problem by considering two
different DM profiles, based on both the fit to the rotation curve (in this
case a Burkert cored profile) and results from N-body cosmological simulations
(i.e., NFW cuspy profile). We also include halo substructures in our analysis,
which is expected to boost the DM signal a factor of ten in halos such as those
of dIrrs. For each DM model and dIrr, we create a spatial template of the
expected DM-induced gamma-ray signal to be used in the analysis of Fermi-LAT
data. No significant emission is detected from any of the targets in our
sample. Thus, we compute upper limits on the DM annihilation cross-section
versus mass parameter space. Among the 7 dIrrs, we find IC10 and NGC6822 to
yield the most stringent individual constraints, independently of the adopted
DM profile. We also produce combined DM limits for all objects in the sample,
which turn out to be dominated by IC10 for all DM models and annihilation
channels, i.e. $b\bar{b}$, $\tau^+\tau^-$ and $W^+W^-$. The strongest
constraints are obtained for $b\bar{b}$ and are at the level of $\langle\sigma
v \rangle \sim 7 \times 10^{-26}\text{cm}^{3}\text{s}^{-1}$ at $m_\chi\sim 6$
GeV. Though these limits are a factor of 3 higher than the thermal relic cross
section at low WIMP masses, they are independent from and complementary to
those obtained by means of other targets.
