KiDS-Legacy: WIMP dark matter constraints from the cross-correlation of weak lensing and Fermi-LAT gamma rays

TL;DR

This study uses 15 years of Fermi-LAT gamma-ray data and KiDS-Legacy weak lensing maps to search for dark matter signals, setting upper limits on WIMP decay and annihilation, and forecasting improved constraints with future surveys.

Contribution

First, it provides new constraints on WIMP dark matter properties through cross-correlation analysis of gamma-ray and weak lensing data, and second, it forecasts the potential of upcoming surveys to tighten these bounds.

Findings

No significant cross-correlation detected.

Established 95% upper bounds on WIMP decay rate and annihilation cross-section.

Forecasted constraints with Euclid-like survey are twice as tight.

Abstract

Dark matter dominates the matter content of the Universe, and its properties can be constrained through large-scale structure probes such as the cross-correlation between the unresolved gamma-ray background (UGRB) and weak gravitational lensing. We analysed 15 years of Fermi-LAT data, constructing UGRB intensity maps in ten energy bins (0.5-1000 GeV), and cross-correlated them with KiDS-Legacy shear in six tomographic bins. The measurements were performed using angular power spectra estimated with the pseudo-$C_\ell$ method. No significant cross-correlation is found. Based on this non-detection, we present 95% upper bounds on the weakly interacting massive particle (WIMP) decay rate $\Gamma_{\rm dec}$ and velocity-averaged annihilation cross-section $\langle\sigma_{\rm ann} v\rangle$ as functions of mass. We compare our results with bounds from other cosmological tracers and from local probes, and found them to be complementary, particularly at low masses ($\rm GeV/TeV$). In addition, using a Euclid-like lensing survey cross-correlated with Fermi-LAT, we forecast $\sim$2 times tighter limits, highlighting the potential of forthcoming data to strengthen constraints on dark matter annihilation and decay.