Search for Gamma-Ray Lines towards Galaxy Clusters with the Fermi-LAT

TL;DR

This study searched for gamma-ray lines in galaxy clusters using Fermi-LAT data to detect potential dark matter signatures, but found no significant signals and set upper limits on dark matter interaction cross sections.

Contribution

First comprehensive search for gamma-ray lines in galaxy clusters with Fermi-LAT, providing constraints on dark matter properties from these large structures.

Findings

No significant gamma-ray line features detected.

Upper limits set on dark matter annihilation cross sections.

Results are consistent with limits from Galactic Center observations.

Abstract

We report on a search for monochromatic $\gamma$-ray features in the spectra of galaxy clusters observed by the \emph{Fermi} Large Area Telescope. Galaxy clusters are the largest structures in the Universe that are bound by dark matter (DM), making them an important testing ground for possible self-interactions or decays of the DM particles. Monochromatic $\gamma$-ray lines provide a unique signature due to the absence of astrophysical backgrounds and are as such considered a smoking-gun signature for new physics. An unbinned joint likelihood analysis of the sixteen most promising clusters using five years of data at energies between 10 and 400 GeV revealed no significant features. For the case of self-annihilation, we set upper limits on the monochromatic velocity-averaged interaction cross section. These limits are compatible with those obtained from observations of the Galactic Center, albeit weaker due to the larger distance to the studied clusters.