Histograms of the ratio of the standard deviationof sightline velocity (σ_proj, top, already presented in central panel of Fig. 4, std stands for standard deviation) and sightline velocity dispersions (σ_los, bottom) of one hundred random projections over the 1D velocity dispersion of the 3D velocity field, σ_sim² = (σ_x² + σ_y² + σ_z²)/3. For each row, we present the ratio of the quantities estimated within R₂₅₀₀ in orange for the EW projections (cyan for MW), R₅₀₀ in red for the EW projections (blue for MW) and R_vir in dark red for the EW projections (dark blue for MW). The mean (median) of the distributions is displayed as dashed (dotted) vertical lines in the same colours and can be compared to one displayed as a dashed grey vertical line.