# SDSS J1640+1932: a spectacular galaxy-quasar strong lens system

## TL;DR

This paper reports detailed observations and modeling of a galaxy-quasar strong lens system, revealing its mass distribution, magnification, and time delay, contributing valuable data to gravitational lensing studies.

## Contribution

First detailed imaging and modeling of SDSS J1640+1932 as a galaxy-quasar strong lens system with precise mass and time delay measurements.

## Key findings

- Einstein radius of 2.49 arcseconds
- Magnification factor of 23 for quasar and host galaxy
- Time delay of approximately 24 days

## Abstract

We present Canada-France-Hawaii Telescope (CFHT) MegaCam observations of a galaxy-quasar strong gravitational lens system, SDSS J1640+1932. This system, located at z=0.195 (foreground elliptical galaxy) and z=0.778 (background quasar), was first visually identified by us in the Sloan Digital Sky Survey (SDSS) database. Our CFHT imaging with an angular resolution of 0.7$^{\prime \prime}$ clearly resolves 4 lensed images and a nearly complete Einstein ring. Modeling the system with a singular isothermal ellipsoid (SIE) total mass distribution, we find an Einstein radius of ${2.49^{\prime \prime}}_{-0.049}^{+0.063}$ enclosing a inferred mass of $7.25_{-0.29}^{+0.37}\times10^{11} M_{\odot}$. The quasar and its host galaxy have been magnified by a factor of 23, and the time delay relative to the leading image is determined to be 23.4-25.2 days. These parameters vary minimally when our model is fitted to the {\it{g}}-, {\it{r}}- or {\it{i}}-band images.