Comparison between the approximate image plane spectrum and source plane spectrum of the CO(6−5) emission in G09v1.97. Left: Source plane moment-0 map of the CO(6−5) emission with the different regions used for the source plane spectral extraction. Right: Normalized source plane spectrum (in yellow) compared to the normalized image plane spectrum (in grey) extracted from the region used in ^3DBAROLO modeling (top), a northern region of the source located inside the caustic line (middle), and a southern region of the source located outside the caustic line (bottom). Note: the per-channel values are the normalized sum in a specific region as described in Sect. 4.1.1 and not a standard flux. The error bars are shown for each channel. Single Gaussian profiles are shown in red, while double Gaussian profiles are shown in blue.