Improved dark matter measurements with studies of realistic strongly lensed quasar narrow-line emission

A key difference among dark matter models lies in their predictions for the halo-mass function and density profiles of low-mass dark matter halos. The relative brightnesses of strongly lensed quasar images, called flux ratios, can respond to perturbations caused by low-mass dark matter halos. We use the quasar narrow-line region (NLR) as a light source for flux ratio studies because it has a size scale that is both sensitive to low-mass perturbations while remaining resilient to microlensing by stars. In previous dark matter studies, a Gaussian distribution has been used to model the NLR light profile, however, observations at low redshifts reveal that narrow-line regions can contain more complex structures beyond Gaussian light distributions. We introduce a novel technique for simulating and measuring flux ratios of realistic strongly lensed NLRs, drawing from nearby quasars. We examine the influence of asymmetric morphologies on observed flux ratios, sensitivity to detecting extended emission, and ultimately its implications for dark matter measurements. This new pipeline can be used to measure dark matter signals in the thousands of lenses which will be discovered in the future in LSST/Euclid missions, for which narrow-line flux ratios will be measured with OSIRIS at Keck.