Relation between median H i linewidth and maximum circular velocity of the dark matter halo. Points are colour coded by the parameter indicated in the top left corner of each panel. The number at the top left corner is the correlation coefficient between said parameter and |$W_{50}^{\mathrm{ med}}/2$| and |${V_{\rm max}^{\rm DMO}}$|⁠. Structural parameters: logarithmic slope of the outer circular velocity profile (top left); H i-to-virial radius (top middle); minimum minor-to-major H i axis ratio (top right). Kinematic parameters: skewness of the linewidth distribution (bottom left); rotation-to-dispersion ratio (bottom middle); and linewidth profile shape (bottom right). Each colour corresponds to a quartile of the distribution (red are the largest 25 per cent, while blue are the smallest 25 per cent), the mean of each quartile is indicated by the coloured numbers.