Meudon PDR modeling of CO lines. As in Fig. 14, all plots presented here are for the region at (RA, Dec) = (05^h39^m43^s,−69°45′43′′) ([−1, 1] in Figs. 8 and 12). The left and right panels are for G_X = 0 and G_X = 10 respectively. Top: CO SLEDs: observations (gray) vs. model predictions (red). The CO predictions are from the best-fit solutions in the top panels of Fig. 14 and are too low to be shown for G_X = 0. For an easy comparison with the observed SLEDs, the model SLEDs are also scaled to match the CO(1–0) integrated intensities and are presented in blue. Middle: model results for the line ratios (A_V = 0.5 mag): CO(3–2)/CO(1–0) (blue), CO(6–5)/CO(3–2) (red), and CO(9–8)/CO(6–5) (green). Each of the observed line ratios is shown as the solid line, while the 1σ uncertainty is the dotted line. Note that the circular contours in the middle left plot at P/k> 10⁷ K cm^-3 and G_UV ~ 500 are artifacts due to the unavailability of model predictions over the corresponding parameter space. Bottom: same as the middle panels, but with A_V = 3 mag. Likewise, the ellipsoidal contour in the bottom right plot at P/k< 10⁵ K cm^-3 and G_UV ~ 30 is simply an artifact. Note that the observed CO(9–8)/CO(6–5) ratio is not reproduced over the entire parameter space.