Tomographic-spectral approach for dark matter detection in the cross-correlation between cosmic shear and diffuse gamma-ray emission

TL;DR

This paper introduces a tomographic-spectral cross-correlation method between cosmic shear and gamma-ray emission to improve dark matter detection sensitivity, demonstrating promising results for current and future surveys.

Contribution

It presents a novel tomographic-spectral approach that enhances dark matter detection prospects by leveraging redshift and energy binning in cross-correlation analyses.

Findings

Potential 5-sigma detection of dark matter with Fermi LAT and DES data for certain parameters.

Forecasts Euclid and future gamma-ray detector data to measure dark matter mass with 1.5-2 times uncertainty.

Method significantly improves sensitivity even for faint dark matter signals.

Abstract

We recently proposed to cross-correlate the diffuse extragalactic gamma-ray background with the gravitational lensing signal of cosmic shear. This represents a novel and promising strategy to search for annihilating or decaying particle dark matter (DM) candidates. In the present work, we demonstrate the potential of a tomographic-spectral approach: measuring the cross-correlation in separate bins of redshift and energy significantly improves the sensitivity to a DM signal. Indeed, the technique proposed here takes advantage of the different scaling of the astrophysical and DM components with redshift and, simultaneously, of their different energy spectra and different angular extensions. The sensitivity to a particle DM signal is extremely promising even when the DM-induced emission is quite faint. We first quantify the prospects of detecting DM by cross-correlating the Fermi Large Area Telescope (LAT) diffuse gamma-ray background with the cosmic shear expected from the Dark Energy Survey. Under the hypothesis of a significant subhalo boost, such a measurement can deliver a 5-sigma detection of DM, if the DM particle is lighter than 300 GeV and has a thermal annihilation rate. We then forecast the capability of the European Space Agency Euclid satellite (whose launch is planned for 2020), in combination with an hypothetical future gamma-ray detector with slightly improved specifications compared to current telescopes. We predict that the cross-correlation of their data will allow a measurement of the DM mass with an uncertainty of a factor of 1.5-2, even for moderate subhalo boosts, for DM masses up to few hundreds of GeV and thermal annihilation rates.