Mg II k/h line ratio against physical parameters for the isothermal isobaric (left column) and PCTR (with γ = 2, right column) models. First row: k/h line ratio vs. T (left) or T_cen (right), colour scale indicates pressure. Second row: k/h line ratio vs. P (left) or P_cen (right), colour scale indicates temperature. Third row: k/h line ratio vs. D (left) or M (right), colour scale indicates temperature. Bottom row: k/h line ratio vs. τ_h, colour scale indicates temperature.