Maps of the blue- (solid contours) and red-shifted (dashed) emission in the CH₃CN(12–11) K = 4 line overlayed on the bulk emission (gray scale) in the same line. The integration was performed over the velocity ranges 88.9–91.3 km s^-1, 100.9–103.3 km s^-1, and 95.2–96.7 km s^-1, respectively. Contour levels increase from 0.15 in steps of 0.27 Jy/beam for the blue- and red-shifted gas, and from 0.2 in steps of 0.2 Jy/beam for the bulk emission. The synthesized beam of the images is drawn in the bottom left. The two white points mark the positions of the two compact free-free sources detected by Cesaroni et al. (2010).