Kinematics of the H I, separated by N(DNM). Left panel: shown separately are the mean H I profiles for the two groups of sources according to their N(DNM): H I emission in the group having more DNM is plotted as a red histogram and emission in the other group is shown as a blue line. Also shown is the mean HCO⁺ optical depth profile for all sources scaled upward by a factor 150. Right panel: as in left panel but the H I profile plotted in orange is the difference of the H I profiles shown in left panel. The greatest difference between the H I profiles coincides with the peak of the HCO⁺ optical depth.