Determination of the launch radii of the maser streamlines. (a) The streamline to which each panel refers is indicated in the top-left corner of the panel. Maser labels (see Table 1) and error bars indicate the values (and corresponding errors) of the angular velocity of the launch radius inferred with the masers belonging to the streamline, which are plotted versus the position along the sky-projected jet axis xl. The dashed blue line and error bar give the mean and standard deviation of the consistent values, excluding the outliers denoted with red labels. (b) Vertical and horizontal error bars plot the values (and associated errors) of the angular velocity and rotation radius of the streamlines. The heavy and thin curves are the Keplerian profiles evaluated at three different YSO masses, as labeled. The launch radius of each streamline for the nominal value of the YSO mass of 5.6 M_⊙ is identified with horizontal and vertical dotted lines, and the associated measurement error is marked by the horizontal error bar in the bottom.