Spatial distribution of the properties of the line center shift of the residual [C II] line with respect to ¹²CO (1−0) (left), to [N II] (middle), and to [C II] (right), as described in Sect. 6.2. The positions with no residual [C II] are diagonally hatched. The baseline RMS of the residual [C II] line is between 42 and 98 mK. The spatial resolution is 14′′ and 18′′ for [C II] and [N II], respectively.