Rotational diagram from the low- J (with solid points in the left panel with E_up < 100 K) and high- J (with solid points in the right panel with E_up > 100 K) transitions shown in Fig. 1 and listed in Table 1, taking the contributions of the three line components into account. The green, orange, and purple points correspond to components C1, C2, and C3, respectively. The solid coloured lines represent a linear regression fit of the points corresponding to the same component, and the final N and T_ex are shown in the upper right corner. For the low-J rotational diagram, the high-J points are shown with lighter colours for completeness, and vice versa.