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: $ \theta_E = 1{{{\overset{\prime\prime}{.}}}}208 $, zs = 3.105; $ \theta_E = 0{{{\overset{\prime\prime}{.}}}}749 $, and zs = 2.395. The six dual quasars have redshifts ranging from 0.58 to 3.28 and projected separations ranging from 15.44 to 22.54 kpc, with a mean separation of 17.95 kpc. The eleven projected quasars have projected separations ranging from 10.96 to 39.07 kpc, with a mean separation of 22.64 kpc. Additionally, there are three likely lensed quasars that cannot be definitively confirmed, included for two reasons. Firstly, their image separations (0$ {{{\overset{\prime\prime}{.}}}} $83, 0$ {{{\overset{\prime\prime}{.}}}} $98, and 0$ {{{\overset{\prime\prime}{.}}}} $93) are small compared to the seeing conditions during our observations (around 1$ {{{\overset{\prime\prime}{.}}}} $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.