Annihilation vs. Decay: Constraining Dark Matter Properties from a Gamma-Ray Detection in Dwarf Galaxies

TL;DR

This paper proposes a method to distinguish between dark matter annihilation and decay signals in gamma-ray observations of dwarf galaxies by analyzing the angular distribution and energy spectrum, aiding in understanding dark matter properties.

Contribution

It introduces a novel strategy to differentiate dark matter annihilation from decay using spatial and spectral analysis of gamma-ray signals, which was not previously feasible with spectrum alone.

Findings

Angular dependence helps identify the origin of gamma-ray signals.

Energy spectrum analysis alone cannot distinguish annihilation from decay.

Potential to infer dark matter substructure presence.

Abstract

Although most proposed dark matter candidates are stable, in order for dark matter to be present today, the only requirement is that its lifetime is longer than the age of the Universe, t_U ~ 4 10^17 s. Moreover, the dark matter particle could be produced via non-thermal processes and have a larger annihilation cross section from the canonical value for thermal dark matter, <sigma v> ~ 3 10^{-26} cm3/s. We propose a strategy to distinguish between dark matter annihilation and/or decay in the case that a clear signal is detected in future gamma-ray observations of Milky Way dwarf galaxies with gamma-ray experiments. The discrimination between these cases would not be possible in the case of the measurement of only the energy spectrum. We show that by studying the dependence of the intensity and energy spectrum on the angular distribution of the signal, the origin of the signal could be identified, and some information about the presence of substructure might be extracted.