C¹⁸O (2−1) line profile. The unaltered spectral profile (black) is overlaid with a portion of the spectral profile mirrored about 4.0 km s^-1 (orange). Light blue areas mark the widths obtained from the best- fit thin disk model (Table 3) of the foreground material (1.6 and 3 km s^-1) and the envelope (4.0 km s^-1). The horizontal line between 5 and 6.5 km s^-1 shows the velocity range used for the UV-space PV diagram.