Gamma rays from dark matter subhalos in the

In the case that dark matter consists of weakly interacting massive particles (WIMPs), dark matter subhalos in the Milky Way could be detectable as gamma-ray point sources due to WIMP annihilations. In this thesis, we study the detectability of dark matter subhalos with Fermi-LAT. We improve on previous work in two ways. Firstly, we take into account the effects of baryons on the density profile within subhalos by adopting a profile recently proposed by Di Cintio et al. Secondly, we use the results of the Via Lactea II simulation — scaled to the latest cosmological parameters — to predict the local dark matter subhalo distribution, instead of making assumptions on the effects of tidal stripping. We find that baryons have a negligible effect on the detectability of point-like subhalos, and we predict that about 3 subhalos are present in the Fermi-LAT point-source catalog 3FGL in the case of a 40 GeV WIMP annihilating to bb at a thermal cross-section. This result is in conflict with the result recently found by Bertoni et al. due to their optimistic treatment of tidal effects. Along with our predictions for the detectability of subhalos, we use the number of subhalo candidate sources in 3FGL based on a spectral analysis presented by Bertoni et al. to place upper limits on the WIMP annihilation cross-section. In case there would be no candidate sources in 3FGL, our constraints are competitive with those found by other studies. Using an optimistic flux threshold, we also predict that about 5 subhalos would be present in 3FGL in the case of a 100 GeV WIMP annihilating to bb at a thermal cross-section — a scenario that has not yet been excluded by current constraints. In addition, adopting the profile proposed by Di Cintio et al., we calculate the J-factor (which parameterises the expected gamma-ray flux resulting from WIMP annihilations in an astrophysical object independently of the exact choice of WIMP particle model) for some of the dwarf galaxies used in the combined dwarf analysis of the Fermi-LAT collaboration. We find that for two of them, the J-factors exceed the error margin quoted in the FermiLAT analysis. This suggests that the upper limits on the annihilation cross-section placed in this analysis are not very robust against the choice of density profile.