Fermi Gamma-ray Space Telescope

A Search for Dark Matter Annihilation in Dwarf Spheroidal Galaxies with Pass 8 Data

Brandon Anderson
Matthew Wood, Alex Drlica-Wagner on Behalf of the Fermi-LAT Collaboration


Dwarf spheroidal galaxies of the Milky Way are a compelling target for indirect dark matter (DM) searches due to their large DM content and the absence of strong astrophysical foregrounds in their vicinity. The Fermi Large Area Telescope (LAT) is sensitive in an energy range from 20 MeV to more than 300 GeV and is well-suited to search for gamma rays produced by the annihilation or decay of DM particles in these objects. Limits derived from a combined likelihood analysis of dwarf galaxies using four years of LAT data from the P7REP release currently provide some of the most stringent constraints on the annihilation cross section of the DM particle. We report on a new analysis of dwarf spheroidal galaxies using the same combined likelihood methodology applied to five years of LAT data reprocessed with an improved event-level reconstruction (Pass 8). Pass 8 improves the LAT performance in several key areas including effective area, point spread function, and energy reach. These improvements enhance the sensitivity to DM annihilation signatures and opens additional parameter space for LAT DM searches.