Constraints on the identity of the dark matter from strong gravitational lenses

TL;DR

This paper demonstrates that analyzing strong gravitational lensing can effectively differentiate between cold and warm dark matter models by detecting subhalo populations, with implications for understanding dark matter particle properties.

Contribution

It introduces a method using mock lensing observations to distinguish CDM from WDM, especially sterile neutrino models, based on subhalo detection thresholds.

Findings

Approximately 100 strong lens systems can differentiate CDM from WDM.

Detection limit of $10^7 h^{-1} M_{}$ is sufficient for model discrimination.

Sterile neutrino WDM models can be tested with upcoming lensing observations.

Abstract

The cold dark matter (CDM) cosmological model unambigously predicts that a large number of haloes should survive as subhaloes when they are accreted into a larger halo. The CDM model would be ruled out if such substructures were shown not to exist. By contrast, if the dark matter consists of warm particles (WDM), then below a threshold mass that depends on the particle mass far fewer substructures would be present. Finding subhaloes below a certain mass would then rule out warm particle masses below some value. Strong gravitational lensing provides a clean method to measure the subhalo mass function through distortions in the structure of Einstein rings and giant arcs.Using mock lensing observations constructed from high-resolution N-body simulations, we show that measurements of approximately 100 strong lens systems with a detection limit of $10^7 h^{-1} M_{\odot}$ would clearly distinguish CDM from WDM in the case where this consists of 7 keV sterile neutrinos such as those that might be responsible for the 3.5 keV X-ray emission line recently detected in galaxies and clusters.