CO(3-2)/CO(2-1), CO(6-5)/CO(2-1), and CO(6-5)/CO(3-2) line ratio maps shown in the left, middle, and right panels, respectively. The color ranges from 0.1 to the maximum ratio for each plot. In the left panel, the contours span the same extent as the color bar with levels 0.1σ, 0.2σ, 0.4σ, 0.8σ, 1σ, 1.5σ, 2σ, 4σ, 6σ, 8σ, and 10σ where 1σ = 2.141273, the root-mean-square value from each ratio map. For the middle panel, the contour levels are 0.1σ, 0.2σ, 0.4σ, 0.8σ, 1σ, 1.5σ, 2σ, 3σ, 4σ, and 5σ with 1σ = 4.712347. The right panel contains contours with levels 0.05σ, 0.1σ, 0.2σ, 0.4σ, 0.6σ, 1σ, 1.5σ, 2σ, 3σ, 4σ, and 6σ, where 1σ = 5.144535. The symbols and markers for all panels are the same as in Fig. 1.