First lensed quasar systems from the VST-ATLAS survey: one quad, two doubles and two pairs of lensless twins

TL;DR

This study identifies and analyzes the first gravitationally lensed quasar systems from the VST-ATLAS survey, including a quad, doubles, and lensless twins, using follow-up spectroscopy.

Contribution

First identification of lensed quasar systems from VST-ATLAS survey, including detailed spectroscopic analysis and classification of lensing candidates.

Findings

One quadruply lensed quasar detected

Two doubly lensed systems identified

Two lensless twin candidates with similar spectra

Abstract

We have analyzed images from the VST ATLAS survey to identify candidate gravitationally lensed quasar systems in a sample of WISE sources with W1 - W2 > 0.7. Results from followup spectroscopy with the Baade 6.5 m telescope are presented for eight systems. One of these is a quadruply lensed quasar and two are doubly lensed systems. Two are projected superpositions of two quasars at different redshifts. In one system two quasars, though at the same redshift, have very different emission line profiles, and constitute a physical binary. In two systems the component spectra are consistent with the lensing hypothesis, after allowing for micro-lensing. But as no lensing galaxy is detected in these two, we classify them as lensless twins. More extensive observations are needed to establish whether they are in fact lensed quasars or physical binaries.