As in Fig. 4 but for the C³⁴S J = 5–4 line (E_u = 28 K). Left panel: black contours show the velocity-integrated intensity with levels ranging from 10 to 90% of 0.8 Jy beam⁻¹ km s⁻¹ in steps of 10%. Right panel: horizontal and vertical white continuous lines, and the blue curves mark, respectively, the V_LSR and positional offset of the YSO, and the Keplerian profile around a YSO of 10 M_⊙. The two horizontal and vertical, white dashed lines indicate the maximum interval of variation for the YSO V_LSR and positional offset, respectively, estimated by eye whilst looking at the symmetrical patterns of the P–V plot. We note that the plotted offset range is larger than for the P–V plots of Figs. 4 and 5.