Top left panel: comparison between the “true” stellar masses of the simulated disc galaxies (x-axis) and those derived via the decomposition of their synthetic rotation curve (y-axis). EAGLE (IllustrisTNG) galaxies are shown as blue triangles (orange squares). Error bars are given from the difference between the 84th and 16th percentiles in the posterior probability distributions. The dashed line shows the one-to-one relation. Top right panel: same, but for the halo masses. Bottom panels: plot of f_⋆ − M_⋆ for the simulated discs using stellar and halo masses from rotation curve decomposition. Colours and symbols are shown as in Fig. 2.