Left: position-inverted-velocity (PIV) diagram of the uvmodelfit peaks in the C¹⁷O emission centred at IRS7B. The inverted velocity axis is used to make the origin of the diagram correspond to the central object. Blue dots are used for the ν∝ r^−1/2 and ν∝ r^-1 fits, green dots for the ν∝ r fit. The velocities are given relative to the centroid velocity, which has a ν_LSR = 6.2 km s^-1. The solid and dashes lines as in Fig. 5. Right: position residuals of the blue (high velocity) data points plotted versus inverse velocity for the two models (Keplerian rotation and infall under conservation of angular momentum), zoomed in to the dashed part of the left panel.