(a) PV diagram of ¹²CO (1–0) across F2 indicated by the magenta dashed line in Fig. 3f. The overlaid contours represent the PV diagram of ¹³CO (1–0). The contours start at 0.9 K (3σ) and increase by 0.9 K. The offsets are given with respect to the southwestern end of the PV cut. The systemic velocities of L1188a and L1188b are indicated by two blue vertical dashed lines. (b) Similar to a, but for ¹²CO (2–1). (c) Similar to a, but for ¹²CO (3–2).