Confirming lensed-quasar candidates with DESI and P200 spectroscopy I. 14 lensed quasars and 8 lensed galaxies

Abstract

Lensed quasars are powerful probes of cosmology, the co-evolution of supermassive black holes and their host galaxies, and the distribution of dark matter. We cross-match 1,724 previously identified candidates from KiDS, HSC, and the DESI Legacy Imaging Surveys (DESI-LS) with DESI DR1, obtaining 937 DESI spectra for 677 unique systems. Combining DESI spectroscopy with observations from the Palomar 200-inch Double Spectrograph (P200/DBSP), we confirm two lensed quasars with source redshifts $z_s={1.93,3.23}$ and Einstein radii $\theta_{\rm E}={0.39,1.07}$ arcsec, respectively. We further identify 12 likely lensed quasars that are well reproduced by a simple SIE model, exhibit lens galaxies in the image modeling, and have at least one available spectrum; across these, $\theta_{\rm E}$ spans $045$-$2.34$ arcsec and $z_s$ spans $1.13$-$2.88$. In 9 of the 12 cases, the systems already satisfy our lensing criteria except that only one quasar image currently has a spectrum; obtaining a second spectrum for the other image would enable immediate confirmation. Moreover, we report eight new static strong lenses spanning galaxy- to group- scale lenses. These results provide valuable targets for follow-up studies and underscore the efficiency of wide-field spectroscopic surveys such as DESI in confirming gravitationally lensed quasars and galaxies.