PV diagrams of C18O (2–1) along four cuts with a P.A. of 0°, 45°, 90°, and 135° (labeled in Figure 1) of the ringlike structure. The gray lines indicate the fitting results from HNC (1–0) (Figure 3). Contour levels are set at 10σ, 20σ, 30σ, and 40σ, where σ = 0.007 Jy beam−1.
