PV diagrams similar to Fig. 9b but for HCN (1–0) (panel a), N₂ H⁺ (1–0) (panel b), and two CH₃OH lines (panel c). In panel a, the three hyperfine structure components are labeled next to their respective emission. In panel b, the channel width of the N₂H⁺ (1–0) spectra has been binned to 0.16 km s⁻¹ to achieve a higher dynamical range in individual channels. In panel c, the two transitions are labeled next to their respective emission. In all panels, the color bars represent main beam brightness temperatures in units of K. The offsets are given with respect to the center of the PV cut (α_J2000 = 18^h28^m50.^s865, δ_J2000 = 00°50′21. ′′799, also indicated by the white filled circle in Fig. 9a), and increase from southeast to northwest. In all panels, the vertical dashed lines mark the systemic velocity of −8.11 km s⁻¹ for corresponding lines.