Constraining decaying very heavy dark matter from galaxy clusters with 14 year Fermi-LAT data

TL;DR

This study uses 14 years of Fermi-LAT gamma-ray data from galaxy clusters to set new constraints on the lifetime of very heavy decaying dark matter particles, considering various decay channels and electromagnetic cascades.

Contribution

It provides the first comprehensive constraints on decaying very heavy dark matter in galaxy clusters using long-term gamma-ray observations and detailed cascade modeling.

Findings

Lower limits on dark matter lifetime range from 10^{25} to 10^{28} seconds.

Constraints are competitive with and complementary to other gamma-ray searches.

Electromagnetic cascades significantly affect the gamma-ray signals from decaying dark matter.

Abstract

Galaxy clusters are promising targets for indirect detection of dark matter thanks to the large dark matter content. Using 14 years of Fermi-LAT data from seven nearby galaxy clusters, we obtain constraints on the lifetime of decaying very heavy dark matter particles with masses ranging from $10^3$ GeV to $10^{16}$ GeV. We consider a variety of decaying channels and calculate prompt gamma rays and electrons/positrons from the dark matter. Furthermore, we take into account electromagnetic cascades induced by the primary gamma rays and electrons/positrons, and search for the resulting gamma-ray signals from the directions of the galaxy clusters. We adopt a Navarro-Frenk-White profile of the dark matter halos, and use the profile likelihood method to set lower limits on the dark matter lifetime at a 95% confidence level. Our results are competitive with those obtained through other gamma-ray observations of galaxy clusters and provide complementary constraints to existing indirect searches for decaying very heavy dark matter.