Coarse-grained channel-by-channel comparison of the reconstruction of line emissions. The content of each sub-panel is like in Fig. 5. From left to right: observed data (image plane), model-predicted image plane reconstruction, difference of these images, and right, model-predicted source plane reconstruction, successively for the CO(6–5) and H₂O(2₁₁−2₀₂) lines. Sub-panels in Cols. 1,2,3,5,6,7 exhibit critical lines whereas the ones in Cols. 4,8 show caustic lines. From top to bottom: line emission channels are ordered with decreasing radial velocity, starting from −530 km s⁻¹ (the beginning velocity of each bin), in steps of 105 km s⁻¹. Throughout those channel maps, no residual above the ±3σ limit are found.