Scatter plot of model vs. data for photoionization models for O defined in Eq. (A.6) (top row), Eq. (A.7) (second row from the top), Eq. (A.7) (third row from the top), and Eq. (A.8) (bottom row); fit residuals (middle column); histograms of the residuals (right column). The red y = x lines are eye guides. The statistical uncertainties of the models are indicated in the insets in the histogram panels.