Distributions of the simulated ‘true’ galaxy parameters measured in the Euclid Morphology Challenge. Top left: I_E distribution down to 5σ detections. Top right: effective radii for the single component galaxy (blue), and for bulges (orange), and discs (green) separately. Middle Left: Axis ratio distributions. Middle right: Sérsic index distributions for single-component galaxies. We note that Sérsic indices of the bulges are fixed to n = 4, and the discs to n = 1. Bottom left shows the bulge-to-total ratio distribution. The black solid line shows the COSMOS distribution. We also note that for b/t, the y-axis is on a logarithmic scale. The distributions are normalised such that the area is equal to 1. This figure is replicated from EMC2023.