Corner plot of χ² surface as a function of the model parameters (Δη, ζ_w) for the highest μ_g bin MAGMA, here with a higher boundary than in Fig. 5: μ_g > 0.75. As in previous figures, the violet contours correspond to the minimum χ² value, and the top and right panels report the probability density distributions for the marginalized parameters. Confidence intervals (±1σ) are shown as violet-tinted shaded rectangular regions, and the MLE (PDF mode for Δη, median for ζ_w) is shown by a vertical dashed line.