Varstrometry for Off-nucleus and Dual sub-Kpc AGN (VODKA). SDSS J1608+2716: A Sub-arcsec Quadruply Lensed Quasar at z=2.575

TL;DR

This study uses HST imaging to confirm that SDSS J1608+2716 is a quadruply lensed quasar at high redshift, demonstrating the importance of deep IR imaging for identifying complex quasar systems.

Contribution

The paper presents the first high-resolution IR imaging confirmation of a quadruply lensed quasar at z=2.575, revealing a fourth component and a lensing galaxy, advancing methods for detecting high-redshift dual/multiple quasars.

Findings

Discovery of a fourth quasar component in the system.

Successful lens modeling with a singular isothermal ellipsoid.

Demonstration of deep IR imaging's role in confirming complex quasar systems.

Abstract

We report Hubble Space Telescope (HST) Wide Field Camera 3 (WFC3) deep IR (F160W) imaging of SDSS J1608+2716. This system, located at a redshift of z=2.575, was recently reported as a triple quasar candidate with subarcsecond separations ($\sim0.25''$) based on selection from Gaia astrometry and follow-up Keck adaptive optics-assisted integral field unit spectroscopy. Our new HST deep IR imaging reveals the presence of a fourth point-like component located $\sim0.9''$ away from the triple system. Additionally, we detect an edge-on disk galaxy located in between the four point sources. The entire system exhibits a characteristic cusp structure in the context of strong gravitational lensing, and the observed image configuration can be successfully reproduced using a lens model based on a singular isothermal ellipsoid mass profile. These findings indicate that this system is a quadruply lensed quasar. Our results highlight the challenges associated with identifying dual/multiple quasars on $\sim$kpc scales at high redshifts, and emphasize the crucial role of deep, high-resolution IR imaging in robustly confirming such systems.