Panel a: C¹⁸O (1–0) integrated intensity map similar to Fig. 2b but overlaid with a PV cut indicated by the white dashed line. Panel b: PV diagram of C¹⁸ O (1–0) along the PV cut in panel a. The channel width of C¹⁸O (1–0) spectra has been binned to 0.1 km s⁻¹ to achieve a higher dynamical range. Panel c: similar to panel b but for HNC (1–0). Panel d: similar to panel b but for CS (2–1). In panels b–d, the color bars represent main beam brightness temperatures in units of K, and the black contours represent the C¹⁸ O (1–0) emission starting at 1.5 K (5σ) with increments of 0.9 K (3σ). 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 panel a), and increase from southeast to northwest. The resolution element is shown in the lower right of each panel.