Astrophysical explanations of suspected dark matter signals in dwarf
  galaxies
  We present methods to assess whether gamma-ray excesses towards Milky Way
dwarf galaxies can be attributed to astrophysical sources rather than to dark
matter annihilation. As a case study we focus on Reticulum II, the dwarf which
shows the strongest evidence for a gamma-ray signal in Fermi data. Dark matter
models and those with curved energy spectra provide good fits to the data,
while a simple power law is ruled out at 97.5% confidence. We compare RetII's
spectrum to known classes of gamma-ray sources and find a useful representation
in terms of spectral curvature and the energy at which the spectral energy
distribution peaks. In this space the blazar classes appear segregated from the
confidence region occupied by RetII. Pulsars have similar gamma-ray spectra to
RetII but we show that RetII is unlikely to host a pulsar population detectable
in gamma rays. Tensions with astrophysical explanations are stronger when
analyzing 6.5 years of Pass 7 than with the same amount of Pass 8 data, where
the excess is less significant. These methods are applicable to any dwarf
galaxy which is a promising dark matter target and shows signs of gamma-ray
emission along its line of sight.
