Scale radii of the total cluster mass density profiles, in units of the virial radii (r_-2/r₂₀₀ on the y-axis) vs. scale radii of the galaxy number density profiles, in the same units (r_{− 2,g}/r₂₀₀ on the x-axis). The error bars are 68% confidence levels, but do not include the uncertainties on r₂₀₀, given that the same quantity is used to normalize both variables on the two axes. The dashed line indicates the identity relation r_-2 ≡ r_{− 2,g}. The solid (red) line indicates the best-fit log-log orthogonal relation between the two quantities, and the (yellow) shaded region indicates its 68% confidence region, obtained via the IDL code confidence_band. The best fit was obtained via the fitting procedure of Williams et al. (2010). Open (respectively filled) dots indicate clusters whose n(R) has been fit with a pNFW (respectively King) model. A2124 is an outlier on this relation and its [r_{− 2,g}/r₂₀₀,r_-2/r₂₀₀] point lies off scale at [5.5,0.23].