Position–velocity diagrams, in units of K(T_MB), of the C¹⁸O(1–0), ¹³CO(1–0), and ¹²CO(1–0) emissions, from left to right. These PV diagrams are perpendicular to the MF filament axis and averaged along its crest. The zero-offset position (on the x-axis) indicates the position of the filament. The black contours correspond to the C¹⁸O(1–0) intensity at 0.3 and 0.5 K, and are the same for the three panels. The three horizontal lines in blue, red, and purple show velocities of 5.4, 6.2, and 7.2 km s⁻¹, respectively. These lines identify the four velocity ranges, B, F1, R1, and R2 described in subsection 3.2. (Color online)