Discovery of 19 strongly-lensed quasars, dual and projected quasars in DESI-LS

TL;DR

This paper reports the spectroscopic confirmation of 2 lensed quasars, 6 dual quasars, and 11 projected quasars, expanding the catalog of known quasar configurations and providing detailed properties for each.

Contribution

It provides the first spectroscopic confirmation of multiple quasar systems identified as candidates, including detailed measurements and analysis of their properties.

Findings

Confirmed 2 lensed quasars with specific Einstein radii and redshifts.

Identified 6 dual quasars with separations from 15.44 to 22.54 kpc.

Detected 11 projected quasars with separations from 10.96 to 39.07 kpc.

Abstract

We report the follow-up spectroscopic confirmation of two lensed quasars, six dual quasars, and eleven projected quasars that were previously identified as lensed-quasar candidates in \cite{He2023}. The spectroscopic data were obtained from two different sources: the P200/DBSP in California and publicly available datasets, including SDSS and DESI-EDR. The two lensed quasars (both pairs) have the following properties: $\theta_E$ = 1.208'', $z_s$ = 3.105; $\theta_E$ = 0.749, $z_s$ = 2.395. The six dual quasars have redshifts ranging from 0.58 to 3.28 and projected separations ranging from 15.44 to 22.54 kpc, with a mean separation of 17.95 kpc. The eleven projected quasars have projected separations ranging from 10.96 to 39.07 kpc, with a mean separation of 22.64 kpc. Additionally, there are three likely lensed quasars that cannot be definitively confirmed, contributed by two reasons. Firstly, their image separations (0.83'', 0.98'', and 0.93'') are small compared to the seeing conditions during our observations (around 1.2''). Secondly, no high SNR lensing galaxy can be detected in the Legacy Survey Imaging. Better spectroscopy and (or) imaging are needed to confirm their lensing nature.