The DELVE Quadruple Quasar Search I. A Lensed Low Luminosity AGN

TL;DR

This paper reports the discovery and analysis of a quadruply lensed, low-luminosity Type 2 AGN at redshift 2.225, using the DELVE survey, follow-up imaging, and spectroscopy, revealing a complex lensing configuration and potential multiple lensing galaxies.

Contribution

First identification of a quadruply lensed low-luminosity AGN with detailed imaging and spectroscopic analysis, highlighting complex lensing features and possible multiple lensing galaxies.

Findings

High predicted magnifications for all four images.

Lensed source is a low-luminosity Type 2 AGN at z=2.225.

Evidence suggests a second lensing galaxy.

Abstract

A quadruply lensed source, J125856.3-031944, has been discovered using the DELVE survey and WISE W1 - W2 colors. Followup direct imaging carried out with the Magellan Baade 6.5 m telescope is analyzed, as is spectroscopy from the 2.5 m Nordic Optical Telescope. The lensed image configuration is kite-like, with the major axis of the lensing galaxy along the symmetry axis of the kite, and with the faintest image at its tail. Redward of 6000 AA the tail image is strongly blended with the lensing galaxy. The Sloan g direct imaging carried out with Magellan permits deblending. As the lensed image configuration is nearly circular, simple models give high predicted magnifications for all four images. The source's narrow emission lines at redshift z=2.225 and low intrinsic luminosity qualify it as a Type 2 AGN. The Magellan image shows a substantial residual that suggests a second lensing galaxy.