Circumscribing Late Dark Matter Decays Model Independently

TL;DR

This paper constrains late dark matter decay models using gamma-ray observations, showing such decays can only account for a small fraction of the unexplained MeV background, independent of specific models.

Contribution

It provides a model-independent upper limit on gamma-ray flux from late dark matter decays based on multiple gamma-ray observations.

Findings

Late dark matter decays contribute at most ~5% to the unexplained MeV background.

Gamma-ray line emission limits from the Galactic Center constrain decay scenarios.

Diffuse photon background measurements restrict the decay rate of dark matter.

Abstract

A number of theories, spanning a wide range of mass scales, predict dark matter candidates that have lifetimes much longer than the age of the universe, yet may produce a significant flux of gamma rays in their decays today. We constrain such late decaying dark matter scenarios model-independently by utilizing gamma-ray line emission limits from the Galactic Center region obtained with the SPI spectrometer on INTEGRAL, and the determination of the isotropic diffuse photon background by SPI, COMPTEL and EGRET observations. We show that no more than ~5% of the unexplained MeV background can be produced by late dark matter decays either in the Galactic halo or cosmological sources.