Anti-correlation between the characteristic halo radius r₋₂ and the characteristic halo density ρ₋₂ for the 160 galaxies of the SPARC sample (left panel: MLconst; right panel: L18a). In this plot the black dots with error bars are the best fit parameters derived from fitting the rotation curves, the red dotted line is the line of Chemin et al. (2011), and the green solid line is the best fit to the data. The green shaded area represents the 1σ uncertainty on this best fit line (confidence interval, which does not represent the intrinsic scatter around the relation).