Combining JWST and Keck OSIRIS to improve strong lensing dark matter measurements

The dark matter model determines the abundance of substructure on sub-galactic scales. Strong lensing provides a way to test the properties of dark matter by probing dark matter structure at these scales. Flux ratios in quasar images denote the varying brightness levels among multiple images created by strong gravitational lensing. Traditionally studies have used the image fluxes of either the narrow-line region measured with Keck OSIRIS, or of the warm dust region measured with JWST. Here we present a new method of measuring the properties of dark matter using simultaneous flux ratio measurements from both sources for the same lens. The framework uses simultaneous flux ratios from these two sources, to measure the shape and amplitude of the halo mass function, including line-of-sight (LOS) haloes and main deflector subhaloes. We show that combining the constraints yields an improved constraint on the properties of dark matter.