DISCOVERY OF FOUR DOUBLY IMAGED QUASAR LENSES FROM THE SLOAN DIGITAL SKY SURVEY

摘要

We report the discovery of four doubly imaged quasar lenses. All the four systems are selected as lensed quasar candidates from the Sloan Digital Sky Survey data. We confirm their lensing hypothesis with additional imaging and spectroscopic follow-up observations. The discovered lenses are SDSS J0743+2457 with the source redshift z_s = 2.165, the lens redshift z_l = 0.381, and the image separation θ = 1."034, SDSS J1128+2402 with z_s = 1.608 and θ = 0."844, SDSS J1405+0959 with z_s = 1.810, zl ≈ 0.66, and θ = 1."978, and SDSS J1515+1511 with z_s = 2.054, zl = 0.742, and θ = 1."989. It is difficult to estimate the lens redshift of SDSS J1128+2402 from the current data. Two of the four systems (SDSS J1405+0959 and SDSS J1515+1511) are included in our final statistical lens sample to derive constraints on dark energy and the evolution of massive galaxies.