Matter in the beam: Weak lensing, substructures and the temperature of dark matter

TL;DR

This paper introduces a novel weak lensing method to distinguish Warm Dark Matter from Cold Dark Matter models by analyzing matter distribution and lensing effects, revealing significant differences in magnification probabilities.

Contribution

The study demonstrates that weak lensing maps can effectively differentiate WDM from CDM, highlighting differences in matter distribution and lensing magnification.

Findings

WDM increases the probability of weak magnifications significantly.

WDM clusters are more homogeneous than CDM clusters.

The differences are detectable through full spatial convergence field analysis.

Abstract

Warm Dark Matter (WDM) models offer an attractive alternative to the current Cold Dark Matter (CDM) cosmological model. We present a novel method to differentiate between WDM and CDM cosmologies, namely using weak lensing; this provides a unique probe as it is sensitive to all the "matter in the beam", not just dark matter haloes and the galaxies that reside in them, but also the diffuse material between haloes. We compare the weak lensing maps of CDM clusters to those in a WDM model corresponding to a thermally produced $0.5$~keV dark matter particle. Our analysis clearly shows that the weak lensing magnification, convergence and shear distributions can be used to distinguish between CDM and WDM models. WDM models {\em increase} the probability of weak magnifications, with the differences being significant to $\gtrsim5\sigma$, while leaving no significant imprint on the shear distribution. WDM clusters analysed in this work are more homogeneous than CDM ones, and the fractional decrease in the amount of material in haloes is proportional to the average increase in the magnification. This difference arises from matter that would be bound in compact haloes in CDM being smoothly distributed over much larger volumes at lower densities in WDM. Moreover, the signature does not solely lie in the probability distribution function but in the full spatial distribution of the convergence field.