Smoothed C¹⁷O(2−1), H¹³CO⁺(4−3), DCO⁺(4−3), N₂H⁺(3−2), and N₂D⁺(3−2) spectra. Overlaid on the C¹⁷O, DCO⁺, N₂H⁺, and N₂D⁺ spectra are the hf-structure fits. The relative velocities of individual hf components in these transitions are labelled with a short bar on the spectra towards IRAS 05399. The H¹³CO⁺ spectra are overlaid with a single Gaussian fit. The fits to the lines at the systemic velocity  ~9 km s^-1 are shown as green lines, whereas the red lines show fits to the lines at lower velocities. Note that H¹³CO⁺(4 − 3) observations were carried out only towards three sources and the line is detected only towards IRAS 05399 and SMM 4 (at  ~1.5 km s^-1).