Fermi-LAT measurement of the diffuse gamma-ray emission and constraints on the Galactic Dark Matter signal

TL;DR

This study uses Fermi-LAT gamma-ray data to search for dark matter signals in the Galaxy, setting limits on dark matter properties and challenging some existing interpretations of cosmic ray anomalies.

Contribution

It provides new constraints on dark matter annihilation or decay signals by modeling astrophysical backgrounds and accounting for uncertainties in cosmic-ray propagation.

Findings

No robust dark matter signal detected.

Set conservative and model-dependent limits on dark matter properties.

Challenges the dark matter interpretation of certain cosmic ray anomalies.

Abstract

We study diffuse gamma-ray emission at intermediate Galactic latitudes measured by the Fermi Large Area Telescope with the aim of searching for a signal from dark matter annihilation or decay. In the absence of a robust dark matter signal, we set conservative dark matter limits requiring that the dark matter signal does not exceed the observed diffuse gamma-ray emission. A second set of more stringent limits is derived based on modeling the foreground astrophysical diffuse emission. Uncertainties in the height of the diffusive cosmic-ray halo, the distribution of the cosmic-ray sources in the Galaxy, the cosmic-ray electron index of the injection spectrum and the column density of the interstellar gas are taken into account using a profile likelihood formalism, while the parameters governing the cosmic-ray propagation have been derived from fits to local cosmic-ray data. The resulting limits impact the range of particle masses over which dark matter thermal production in the early Universe is possible, and challenge the interpretation of the PAMELA/Fermi-LAT cosmic ray anomalies as annihilation of dark matter.