Identification of the condensations C2 and C3 from integrated-intensity maps and their extracted spectra. Left and central panels: colours show the HC₃N(24–23) integrated-intensity maps in the velocity channels 70–75 and 80–85 km s^–1. The orange contours correspond to half of the peak value of the 70–75 km s^–1 map (1.7 Jy km s^–1), and purple contours correspond to half of the peak value the 80–85 km s^–1 map (2.6 Jy km s^–1). The solid white lines represent the directions of the pv diagrams shown in Fig. 8. Right panel: spectrum extracted from the C2 condensation defined by the orange contours in the north (black histogram), and the spectrum extracted from the C3 condensation defined by the purple contours (grey histogram). The dashed vertical green, orange, and purple lines indicate the v_LSR of the three components obtained from the LTE analysis (see Sect. 3.1).