Schematic illustration of the disk-envelope model employed here and by T13. The material inside the centrifugal radius, R_C, rotates with Keplerian velocity (solid arrow), while the material outside R_C is rotating and infalling (dashed arrows). The blue- and redshifted material is shown in blue and red, respectively. The system is 5° inclinded from edge-on, such that the disk and envelope west of the protostar are nearest to the observer.