Azimuthal velocity profile fit. Top left: azimuthal velocity profile extracted from the observed image cube (blue line), from a simulated image cube of a Keplerian model (red line), and the expected Keplerian profile (v_ϕ ∝ r^−1/2, dashed grey line). Bottom left: azimuthal velocity profile residual after subtracting the expected Keplerian profile. The blue- and red-shaded regions represent the 1σ uncertainty. The shaded grey region in the left panels represents the dust arc peak and extent. Top right: velocity map residuals after subtracting the best-fit Keplerian model. Bottom left: velocity map residuals after subtracting a model using the measured non-Keplerian azimuthal velocity profile. The dashed grey lines represent wedges used to fit the data near the disc’s major axis.