Panel a: model moment 1 map (color) that best matches the observations, assuming the gas kinematics traced by the ¹³CO emission is the three-dimensional infalling and rotational motions as described by Eqs. (C.4)–(C.7). Panel b: residual moment 1 map (color) after subtracting the model moment 1 map, panel a from the observed moment 1 map, Fig. 8a. Panel c: ratio of the residuals to the expected relative velocity from the model. The color scale shows the percentages. White and light blue contours present the observed moment 0 maps of the ¹³CO emission at the medium velocities and the C¹⁸O emission, the same as those in Fig. 8. Blue and red arrows show the directions of the blue- and redshifted outflows. Crosses denote the position of HL Tau.