Superposition model of the extended rotating discs (upper panels) and the rotating IGrM model (lower panels). Left panels: Modelled velocity maps with the observed intervening Mg II mean velocities overlaid for each of the four delensed sources. The inset shows the zoom-in on a region encompassing Ci1 and the quasar. Right panels: Model-predicted velocities (orange) at the positions of the Arc, Ci1, Ci2, and the quasar as a function of impact parameter relative to the barycentre, marked by a plus sign in the left panels (superposition model: barycentre of G1–G3; IGrM: G1–G5). The observed Mg II velocities are displayed in black for the Arc, Ci1, and Ci2, and the blue lines and squares are for the quasar.