Probability density distributions of stellar orbits P(λ_Z, t) in the phase space of circularity λ_z vs. age t for Au-6-60-5. Left panel: true distribution directly derived from the simulation. Middle panel: model-recovered distribution from model A. Right panel: model-recovered distribution from model B, which is the average of all acceptable models within the 1σ confidence level. The normalised probability P/P_max is indicated by the colour bar. The horizontal dashed lines divide the cold (λ_z ≥ 0.8), warm (0.25 < λ_z < 0.8) and hot (λ_z ≤ 0.25, including the counter-rotating orbits) components. The solid blue line in each panel represents the mean stellar age as a function of circularity from the simulations, while the dashed blue lines denote the model-recovered ages from models A and B.