Critical curves of three reference lens models. Left: Critical curves for models Img-MP (L) (solid purple line), Esr2-MP_test (L) (solid cyan line), and Img-MP (L/D) (solid green line), and for the redshift of S0. The upper-left inset zooms in on a 5″ × 3″ rectangle to show more details of critical curves in the central region. Right: Same critical curves but for the redshift of S3. The upper-left inset zooms in on an 8″ × 5″ rectangle around the central region where the third image of S3 falls (blue “cross”). No critical curves pass through S3(b), the extended arc of S3, indicating that it comprises a single distorted image.