Top left box: velocity-integrated CO (J = 2−1) line emission in the central 400′′ × 400′′ area (V_LSR range from −41 to −12 km s^-1). Other upper maps: velocity-channel maps (resolution 2 km s^-1); marked velocities are relative to the LSR systemic star velocity (V_∗ = −26.5 km s^-1); the units of the color scale correspond to K km s^-1. Positive and negative velocities correspond to the rear and front parts of the envelope, respectively. Bottom right panels: observed ¹²CO(2−1) line profiles along a strip to the east for Δδ = 0′′; the upper left numbers indicate Δα in arcseconds and the upper right numbers the intensity scaling factor applied to plot all spectra at the same scale (in K). The contribution of the telescope error beam has been removed from the data and is shown in red for each spectrum. Bottom left panel: the ¹³CO (2−1) line emission integrated between V_LSR−28.5 and −24.5 km s^-1 (black contours) superimposed on the ¹²CO emission in the same velocity range. Note that the r = 50′′ shell also appears in ¹³CO. The inner shells are not resolved by the 11′′ beam.