Cross-correlation of weak lensing and gamma rays: implications for the nature of dark matter

TL;DR

This study cross-correlates gamma-ray data with weak lensing surveys to search for dark matter signals, finding no significant correlation but setting new constraints on dark matter properties, especially for low-mass particles.

Contribution

First measurement of tomographic weak lensing cross-correlations with gamma rays and application of spectral binning, providing novel constraints on dark matter annihilation and decay.

Findings

No significant gamma-ray and weak lensing cross-correlation detected.

Constraints exclude thermal relic cross-section for dark matter masses below 20 GeV.

Tomography does not significantly improve dark matter constraints in this analysis.

Abstract

We measure the cross-correlation between Fermi-LAT gamma-ray photons and over 1000 deg$^2$ of weak lensing data from the Canada-France-Hawaii Telescope Lensing Survey (CFHTLenS), the Red Cluster Sequence Lensing Survey (RCSLenS), and the Kilo Degree Survey (KiDS). We present the first measurement of tomographic weak lensing cross-correlations and the first application of spectral binning to cross-correlations between gamma rays and weak lensing. The measurements are performed using an angular power spectrum estimator while the covariance is estimated using an analytical prescription. We verify the accuracy of our covariance estimate by comparing it to two internal covariance estimators. Based on the non-detection of a cross-correlation signal, we derive constraints on weakly interacting massive particle (WIMP) dark matter. We compute exclusion limits on the dark matter annihilation cross-section $\langle\sigma_\rm{ann} v \rangle$, decay rate $\Gamma_\rm{dec}$, and particle mass $m_\rm{DM}$. We find that in the absence of a cross-correlation signal, tomography does not significantly improve the constraining power of the analysis. Assuming a strong contribution to the gamma-ray flux due to small-scale clustering of dark matter and accounting for known astrophysical sources of gamma rays, we exclude the thermal relic cross-section for particle masses of $m_\rm{DM}\lesssim 20$ GeV.