Weak Gravitational Lensing as a Method to Constrain Unstable Dark Matter

TL;DR

Weak gravitational lensing can be a powerful, model-independent method to constrain the stability and lifetime of dark matter particles by analyzing their effects on cosmic shear statistics.

Contribution

This paper demonstrates how weak lensing shear correlations can provide the most restrictive constraints on unstable dark matter, highlighting the need for further theoretical work on nonlinear structure growth.

Findings

Weak lensing statistics are sensitive to dark matter decay effects.

Measurements can constrain dark matter lifetime independently of specific models.

Upcoming surveys will enhance the precision of these constraints.

Abstract

The nature of the dark matter remains a mystery. The possibility of an unstable dark matter particle decaying to invisible daughter particles has been explored many times in the past few decades. Meanwhile, weak gravitational lensing shear has gained a lot of attention as a probe of dark energy. Weak lensing is a useful tool for constraining the stability of the dark matter. In the coming decade a number of large, galaxy imaging surveys will be undertaken and will measure the statistics of cosmological weak lensing with unprecedented precision. Weak lensing statistics are sensitive to unstable dark matter in at least two ways. Dark matter decays alter the matter power spectrum and change the angular diameter distance-redshift relation. We show how measurements of weak lensing shear correlations may provide the most restrictive, model-independent constraints on the lifetime of unstable dark matter. Our results rely on assumptions regarding nonlinear evolution of density fluctuations in scenarios of unstable dark matter and one of our aims is to stimulate interest in theoretical work on nonlinear structure growth in unstable dark matter models.