Position–velocity (PV) diagrams in units of K(T_MB) for the ¹²CO(2-1), ¹³CO(2-1), and C¹⁸O(2-1) emission (from top to bottom). The ¹³CO(2-1) and C¹⁸O(2-1) maps have a spatial resolution of 30.″2. The ¹²CO(2-1) map has a spatial resolution of 90″. These PV diagrams are averaged in latitude across the cloud for 0.″4 = b = 1″. The white contours indicate the C¹⁸O(2–1) intensity at 1 K and are the same for the three panels. In the top panel the thick white contour corresponds to the ¹²CO(2–1) intensity at 0.6 K.