Dark Matter Searches with the Fermi-LAT in the Direction of Dwarf Spheroidals

TL;DR

This study analyzes 6 years of Fermi-LAT gamma-ray data from dwarf spheroidal galaxies to search for dark matter signals, setting strong constraints on dark matter annihilation cross sections, especially for WIMPs below 100 GeV.

Contribution

It provides the most stringent gamma-ray constraints to date on dark matter annihilation from dwarf spheroidal galaxies using Pass 8 data.

Findings

No significant gamma-ray detection in dwarf galaxies.

Upper limits on dark matter annihilation cross section below thermal relic level for certain masses.

Constraints are among the strongest for WIMPs under 100 GeV.

Abstract

The dwarf spheroidal satellite galaxies of the Milky Way are some of the most dark-matter-dominated objects known. Due to their proximity, high dark matter content, and lack of astrophysical backgrounds, dwarf spheroidal galaxies are widely considered to be among the most promising targets for the indirect detection of dark matter via gamma rays. Here we report on gamma-ray observations of Milky Way dwarf spheroidal satellite galaxies based on 6 years of Fermi Large Area Telescope data processed with the new Pass 8 reconstruction and event-level analysis. None of the dwarf galaxies are significantly detected in gamma rays, and we present upper limits on the dark matter annihilation cross section from a combined analysis of the 15 most promising dwarf galaxies. The constraints derived are among the strongest to date using gamma rays and lie below the canonical thermal relic cross section for WIMPs of mass $\lesssim 100~GeV$ annihilating via the $b \bar b$ and $\tau^{+}\tau^{-}$ channels.