Another Quadruply Lensed Quasar from the VST-ATLAS Survey

TL;DR

This paper reports the discovery and analysis of a new quadruply lensed quasar system identified in the VST-ATLAS survey, including spectroscopic confirmation and lens modeling.

Contribution

It introduces a novel method for identifying quadruply lensed quasars using WISE and ATLAS survey data, with detailed follow-up observations and lens modeling.

Findings

Confirmed quasar at z=2.16 with four images.

Estimated lensing magnifications between 6.4 and 10.8.

No significant lensing galaxy detected after PSF subtraction.

Abstract

We report the quadruple nature of the source WISE 025942.9-163543 as observed in the VST-ATLAS survey. Spectra of the two brightest images show quasar emission lines at z=2.16. The system was discovered by splitting ATLAS "cutouts" of WISE sources with W1-W2 > 0.7, when possible, into three components. Followup Magellan images were used to obtain astrometry and g and i photometry, with i=18.78 and 19.73, respectively, for the brightest and faintest components. Absorption lines are observed at z=0.905 but there is little evidence for a lensing galaxy after PSF fitting and subtraction. Saha and Williams (2003) would classify ATLAS 0259-1635 as a short-axis quad. The larger and smaller diameters are 1.57 and 1.32 arcseconds, respectively. Modeling the lensing galaxy as a singular isothermal sphere with external shear, the largest and smallest predicted magnifications are 10.8 and 6.4 respectively.