Fraction of [C II] emission coming from the ionized gas phase. We show predictions for each DGS galaxy based on: (1) the best single or mixed models reported in Tables 3 and 4 (crosses), and (2) the best single or mixed models with one model having a fixed low density of 30 cm⁻³ (circles); predictions yielding (all models are bad) are not plotted. Red symbols indicate that [N II]₁₂₂ is detected and orange symbols indicate that both [N II]₁₂₂ and [N II]₂₀₅ are detected. For the three galaxies where [N II]₂₀₅ is detected, we also show the predicted values from simple theoretical calculations, as done in Croxall et al. (2017). We overlaid the data (diamonds) and fit from Croxall et al. (2017) as well as the prediction from PDR models from Kaufman et al. (2006) in gray. Fits to the DGS data and to the DGS (free density) and Croxall et al. (2017) data are shown in blue.