Improving the Sensitivity of Gamma-Ray Telescopes to Dark Matter Annihilation in Dwarf Spheroidal Galaxies

Understand

The Fermi-LAT collaboration has studied the gamma-ray emission from a stacked population of dwarf spheroidal galaxies and used this information to set constraints on the dark matter annihilation cross section.

• Interestingly, their analysis uncovered an excess with a test statistic (TS) of 8.7.
• If interpreted naively, this constitutes a 2.95 sigma local excess (p-value=0.003), relative to the expectations of their background model.
• In order to further test this interpretation, the Fermi-LAT team studied a large number of blank sky locations and found TS>8.7 excesses to be more common than predicted by their background model, decreasing the significance of their dwarf excess to 2.2 sigma (p-value=0.027).