Position-velocity diagrams along the observed strip (Fig. 1) after continuum subtraction. The origin of the position axis is the IF and the negative direction extend SW of the origin. The dotted white ellipse indicates the size of the H ii region. Black solid contours in the CO panels trace the intensity of ¹²CO (9  →  8) emission from 2 to 37 K, in steps of 5 K. Dashed black contours display the intensity of the C¹⁸O (5  →  4) line from 1 to 6 K in linear steps of 1 K. The white solid contours represent the o-H₂O emission from 0.1 to 0.9 K in steps of 0.2 K.