Marginalised chi-squares χ_norm² = (χ² − χ_min²)/Δχ_CL² as a function of model-recovered bar pattern speeds Ω_p for bar side-on cases (φ_T ≥ 50°). From left to right, the panels show the results for Au-18, Au-23, and Au-28. Each fold line represents a complete set of modelling runs. The red, blue, magenta, black fold lines denote the viewing angles of the mock data sets (θ_T, φ_T) = (85° ,50° ), (85° ,80° ), (89° ,50° ), and (89° ,80° ), respectively. The horizontal dashed lines represent 1σ (68%, χ_norm² = 1) and 2σ (95%, χ_norm² = 2) confidence levels. The vertical dotted lines denote the true bar pattern speeds, with their values shown by the green annotations.