ULAS J234311.93-005034.0: A gravitational lens system selected from UKIDSS and SDSS

TL;DR

This paper reports the discovery of a new gravitational lens system identified using UKIDSS and SDSS data, featuring a doubly imaged quasar and a lensing galaxy likely in a cluster environment, demonstrating the survey's effectiveness.

Contribution

First gravitational lens system selected from UKIDSS and SDSS data, showcasing the survey's potential for discovering new lenses.

Findings

Doubly imaged quasar at redshift 0.788 with 1.4" separation

Lensing galaxy detected with estimated redshift ~0.3

Potential lens in a cluster environment with candidate arc structures

Abstract

We report the discovery of a new gravitational lens system. This object, ULAS J234311.93-005034.0, is the first to be selected by using the new UKIRT Infrared Deep Sky Survey (UKIDSS), together with the Sloan Digital Sky Survey (SDSS). The ULAS J234311.93-005034.0 system contains a quasar at redshift 0.788 which is doubly imaged, with separation 1.4". The two quasar images have the same redshift and similar, though not identical, spectra. The lensing galaxy is detected by subtracting point-spread functions from R-band images taken with the Keck telescope. The lensing galaxy can also be detected by subtracting the spectra of the A and B images, since more of the galaxy light is likely to be present in the latter. No redshift is determined from the galaxy, although the shape of its spectrum suggests a redshift of about 0.3. The object's lens status is secure, due to the identification of two objects with the same redshift together with a lensing galaxy. Our imaging suggests that the lens is found in a cluster environment, in which candidate arc-like structures, that require confirmation, are visible in the vicinity. Further discoveries of lenses from the UKIDSS survey are likely as part of this programme, due to the depth of UKIDSS and its generally good seeing conditions.