Combined RGB plot and channel map and Herschel column density map for NGC7538. Each panel displays the distinct velocity ranges (blue and red for the high-velocity blue- and redshifted emission, green for the bulk emission) as an RGB plot with contours of ¹²CO(2−1) emission overlaid. The contour levels are 4 to 38 K km s⁻¹ in steps of 4 K km s⁻¹. The corresponding CO velocity is given in the upper-right corner. The two exciting stars are indicated with yellow star symbols. A very prominent example of high-velocity redshifted [C II] gas not associated with an expanding bubble is indicated with a red arrow.