Towards a Bullet-proof test for indirect signals of dark matter

TL;DR

This paper proposes a new method using spatial distribution analysis of merging galaxy clusters to robustly test whether signals like the 3.55 keV line originate from dark matter, enhancing indirect detection reliability.

Contribution

It introduces a statistical framework leveraging spatial information from galaxy clusters to validate dark matter signals, improving robustness against astrophysical backgrounds.

Findings

Spatial analysis can distinguish dark matter signals from backgrounds.

Existing observations of the Coma Cluster can test the dark matter origin of the 3.55 keV line.

Deep exposures in merging galaxy clusters are highly motivated for future indirect detection efforts.

Abstract

Merging galaxy clusters such as the Bullet Cluster provide a powerful testing ground for indirect detection of dark matter. The spatial distribution of the dark matter is both directly measurable through gravitational lensing and substantially different from the distribution of potential astrophysical backgrounds. We propose to use this spatial information to identify the origin of indirect detection signals, and we show that even statistical excesses of a few sigma can be robustly tested for consistency--or inconsistency--with a dark matter source. For example, our methods, combined with already-existing observations of the Coma Cluster, would allow the 3.55 keV line to be tested for compatibility with a dark matter origin. We also discuss the optimal spatial reweighting of photons for indirect detection searches. The current discovery rate of merging galaxy clusters and associated lensing maps strongly motivates deep exposures in these dark matter targets for both current and upcoming indirect detection experiments in the X-ray and gamma-ray bands.