Search for gamma-ray line features from Milky Way satellites with Fermi-LAT Pass 8 data

TL;DR

This study analyzes 91 months of Fermi-LAT data to search for gamma-ray line signals from Milky Way satellites, setting new upper limits on dark matter annihilation into photons, but finds no significant signals.

Contribution

First comprehensive search for gamma-ray lines from multiple Milky Way satellites using Pass 8 data, improving constraints over previous analyses.

Findings

No significant gamma-ray line signals detected.

Upper limits on dark matter annihilation cross section derived.

Constraints significantly improved compared to previous Pass 7 results.

Abstract

With 91 months of the publicly available Fermi-LAT Pass 8 data, we analyze the gamma-ray emission from the Milky Way satellites to search for potential line signals due to the annihilation of dark matter particles into double photons. The searched targets include a sample of dwarf spheroidal galaxies, the Large Magellanic Cloud (LMC) and Small Magellanic Cloud (SMC). No significant line emission has been found neither in the stacked dwarf galaxy sample nor in the direction of LMC/SMC. The corresponding upper limits on the cross section of DM annihilation into two photons are derived. Compared with results of previous gamma-ray line searches with the Pass 7 data, the current constraints on the line emission from dwarf spheroidal galaxies has been significantly improved in a wide energy range. With the rapid increase of the sample of dwarf spheroidal galaxies (candidates), we expect that the sensitivity of gamma ray line searches will be significantly improved in the near future.