Combined RGB plot and channel map for S106 and M42. In the first M42 panel, the expanding [C II] bubble is approximated by a dotted circle. 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 ¹³CO(2−1) emission overlaid. The contour levels are 3 to 17 K km s⁻¹ in steps of 2 K km s⁻¹ for S106 and 3 to 20.5 in steps of 3.5 K km s⁻¹for M42. The corresponding CO velocity is given in the upper-right corner. The exciting star is indicated with yellow star symbols.