Top panel: Density profile of the highest-mass DM halo of the Sparkler galaxy as predicted by the models by Correa et al. (2015). Black lines indicate the z = 0 profile while red lines the z = 1.378 one. The dotted lines mark r₋₂, the dashed lines mark r₂₀₀. The grey shaded area marks the region between 1 and 10 kpc, that is the interval under study. Bottom panel: Difference between the halo density profile at z = 0 and at z = 1.378 normalised to the density profile at z = 0.