Observations, models, and residuals of intensity, velocity, and velocity dispersion from the CO(1–0) line. Models are shown both for each disc (columns 2 and 3) and for the two superposed discs (column 4). Residuals are the observation (column 1) minus the two superposed discs (column 4). On the velocity maps of individual discs, iso-line-of-sight velocity curves are represented by dashed (resp. solid) black lines for values below (resp. above) the systemic velocity of the disc.