Rotational diagrams for ¹²CO υ = 1−0 (top left), υ = 2−1 (top right), υ = 3−2 (bottom left), and ¹³CO υ = 1−0 (bottom right). In each panel, the slab models are given by the solid line. For the ¹²CO transitions, the narrow and broad components (NC and BC, respectively) are shown separately. The integrated fluxes for the narrow component are given by the dots, while those for the broad component are indicated by the squares. The two lines in each model correspond the R- and P branches.