Sample simulated mass profile and associated mass decomposition. The data points correspond to a power-law mass distribution with α= 1.8, while the solid line indicates the best-fitting two-component (dark plus luminous matter) model. Error bars, corresponding to a 10 per cent fractional uncertainty, are shown to guide the eye. Also shown are the corresponding best-fitting dark matter (dotted line) and stellar mass (dashed line) models. Note how the sum of two scale-dependent models produces an approximately power-law total mass distribution over the fitted range.