Finding Quasars behind the Galactic Plane. III. Spectroscopic Identifications of ∼1300 New Quasars at ∣<i>b</i>∣ ≤ 20° from LAMOST DR10

Abstract Quasars behind the Galactic plane (GPQs) are excellent tracers to probe the chemistry and kinematics of the interstellar/intergalactic medium of the Milky Way along sight lines via absorption line spectroscopy. Moreover, quasars located at low Galactic latitudes will fill the gap in the spatial distribution of known quasars near the Galactic plane, and can be used to construct an astrometric reference frame for accurate measurements of proper motions of stars, and substructures of the Milky Way. We started a survey of background quasars in the low Galactic latitude region with the LAMOST phase II survey in 2017. Quasar candidates have been selected from the optical and infrared photometric data of the Pan-STARRS1 and Wide-field Infrared Survey Explorer surveys based on their variability and color properties. In this paper, we present a sample of 1982 spectroscopically confirmed GPQs with ∣ b ∣ ≤ 20° based on LAMOST Data Release 10 (DR10). Among them, 1338 are newly discovered. Most GPQs are located around 240° &lt; l &lt; 90°, and the spatial distribution is nonuniform. These GPQs have a magnitude distribution with a peak at i -mag 19.0, and are mostly located around 18.0–19.5 mag. The peak of the redshift distribution is around 1.5, and most of the GPQs have redshifts between 0.3 and 2.5. Our finding demonstrates the potential discovery space for GPQs from spectroscopic surveys and promising applications for future research.