Modeled column density of high-ionization species (color-coded) as a function of the ionization parameter for the different total H I column densities used as stopping criteria for the calculations. The models shown here were ran with log Z/Z_⊙ = −0.9 (median metallicity of the sample) and log n_H/cm⁻² = 2. The dashed-dotted, dashed, and solid lines correspond to log N(H I) = 15, 18, and 21, respectively.