Five representative velocity channels to illustrate where in the system the ¹³CO and C¹⁸O emissionoriginates for the fiducial model with a constant CO/H abundance of 10⁻⁴ . The velocity profile in the disk is Keplerian and the envelope material is rotating and infalling (see Fig. 5). Top panels: material moving at the line-of-sight velocity (with respect to the systemic velocity of 5.9 km s⁻¹) indicated in the top right corner. Material in the disk (dark gray circle) is depicted in dark purple, envelope material in light purple. The solid black line in the middle and bottom panels marks the τ = 1 surface for an observer located on the left (as depicted by the arrow on top of the figure) for ¹³CO and C¹⁸O, respectively.The color scale represents the temperature in the best-fit model from T13 and the dashed line indicates the adopted disk outer radius of 125 au.