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

We report the results of a follow-up spectroscopic confirmation of two lensed quasars, six dual quasars, and eleven projected quasars that had previously been identified as lensed-quasar candidates in our earlier work. The spectroscopic data were obtained from two different sources: Palomar 200-inch Double Spectrograph (P200/DBSP) in California and publicly available datasets, including SDSS and DESI-EDR. The two lensed quasars (both pairs) have the following properties: θE = 1.208, zs = 3.105; θE = 0.749, and zs = 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, included for 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 signal-to-noise (S/N) lensing galaxy can be feasibly detected in Legacy Survey Imaging. Improved spectroscopy and/or imaging would be needed to confirm their lensing nature.