Optimisation results when modelling the three systems from 𝒟₁ with an elliptical power law + external shear. The upper panel (a) shows the results for the unperturbed system, the middle panel (b) for 1 keV, and the lower panel (c) for 3 keV. From left to right: images are the initial data, reconstructed model, normalised residuals between these two images, and reconstructed source. The units are arbitrary, but analogous to a 2D mass density