Sketch of different PDR proportions (c_PDR) in our mixed models. The yellow regions represent H ii regions, and PDRs are represented in gray. The blue arrow indicates the direction of increasing c_PDR. The black arrows show the lines of sight through the represented clouds (each line of sight representing a given pixel in our maps). As per Eq. (4), the 0% c_PDR case corresponds to no PDR in the model, hence fully ionized gas; 50% cPDR corresponds to a single Cloudy model, with a connected H ii region and PDR (Eq. (A.2)); and 100% c_PDR represents a full PDR model, without an H ii region contribution. We note that 50% of PDR does not correspond to a medium with half of the volume being filled by PDR, but corresponds to a mix that can be modeled by a Cloudy model with a full PDR layer.