Lunch talk on Jul. 8, 2024

Testing the Line of Sight Effect in Strong Lensing System from N-body Simulation

Speaker: Shijie Lin (BNU)

Venue: SWIFAR Building 2111

Time: 12:30 PM, Monday, Jul. 8, 2024

Abstract: 

Matter near a gravitational lens galaxy or projected along the line of sight (LOS) can affect strong lensing observables, which is non-negligible in practice. To approximate these effects, one can use external convergence and shear to model perturbations along the LOS. Previous studies have tested the LOS effect by incorporating dark matter halos from complete populations of dark matter subhalos and line-of-sight halos. In this work, we assess the LOS effect using N-body simulations, which provide a more realistic matter distribution. We perform multi-plane raytracing to simulate the strong lensing images of quasars and their host galaxies, modeling the images with both a single-lens model and a lens plus external shear model. Our findings indicate that the lens plus external shear model reproduces realistic images more accurately than the single-lens model alone. The predicted quasar image fluxes from both models exhibit a few percent difference compared to the true fluxes, an effect known as the flux anomaly.