Complementary distribution between L1188a and L1188b observed in ¹²CO (1–0) (left), ¹²CO (2–1) (middle), and ¹²CO (3–2) (right). In all panels, turquoise and red represent the intensity maps integrated from −14 to −11 km s⁻¹ and from −8 to −5 km s⁻¹, respectively.In the right panel, the overlaid contours are the same as those in Fig. 3h. The curved region that shows enhanced ¹³CO emission is indicated by the yellow box, while the centric concave shape of L1188b is indicated by the yellow dashed arc. In each panel, the two pentagrams represent the two 22 GHz water maser positions discussed in Sect. 3.3.