QU-fitting results for a single pixel in R2_N (top) and for a single pixel in R2_S (bottom), assuming the external depolarisation model (EDF, Eq. 8). Left panel: Fits on Stokes I, Q, and U fluxes. Middle panel: Resulting fractional polarisation, p(λ²), and polarisation angle, χ(λ²). Right panel: Corner plot for the distribution of the uncertainties in the fitted polarisation parameters (i.e. p₀, χ₀, RM, and ). The contour levels are drawn at [0.5, 1.0, 1.5, 2.0]σ, with σ as the 68% statistical uncertainty (see dashed lines in the 1D histogram).