Particle dark matter searches outside the Local Group

TL;DR

This paper proposes a novel cross-correlation technique to detect particle dark matter outside the Local Group, demonstrating its higher sensitivity over traditional gamma-ray methods and suggesting potential DM signals around 10-100 GeV.

Contribution

It introduces a new angular cross-correlation method that enhances detection sensitivity for dark matter signals outside the Local Group, outperforming existing gamma-ray probes.

Findings

Cross-correlation method is more sensitive than traditional gamma-ray analyses.

Measured cross-correlation fits a dark matter component with 10-100 GeV mass.

Potential dark matter signals consistent with thermal annihilation cross section.

Abstract

If dark matter (DM) is composed by particles which are non-gravitationally coupled to ordinary matter, their annihilations or decays in cosmic structures can result in detectable radiation. We show that the most powerful technique to detect a particle DM signal outside the Local Group is to study the angular cross-correlation of non-gravitational signals with low-redshift gravitational probes. This method allows to enhance signal-to-noise from the regions of the Universe where the DM-induced emission is preferentially generated. We demonstrate the power of this approach by focusing on GeV-TeV DM and on the recent cross-correlation analysis between the 2MASS galaxy catalogue and the Fermi-LAT gamma-ray maps. We show that this technique is more sensitive than other extragalactic gamma-ray probes, such as the energy spectrum and angular autocorrelation of the extragalactic background, and emission from clusters of galaxies. Intriguingly, we find that the measured cross-correlation can be well fitted by a DM component, with thermal annihilation cross section and mass between 10 and 100 GeV, depending on the small-scale DM properties and gamma-ray production mechanism. This solicits further data collection and dedicated analyses.