PV diagrams of dent 4. The emission at a υ_LSR velocity of +9 km s⁻¹ is the OMC, and the weak [C ii] emission of the Veil is at υ_LSR =−4 km s⁻¹. The dent at 33′ is indicated by a green arrow in the [C ii] 158 μm PV diagram. The ¹²CO and H i PV diagrams are shown in the middle and lower panels, respectively. H i observation from van der Werf et al. (2013) exists in the area between the two dashed red lines, which is 15′ wide, in the [C ii] and CO observations. Dent 4 is located at 7.5′ in the H i PV diagram.