Examples of incident ionizing spectra (in units of the luminosity per unit frequency at the Lyman limit) as a function of photon energy in the AGN and the star-forming galaxy models described in Sect. 6. The beige shaded area highlights the AGN accretion disk ionizing radiation with power-law indices between α = −2.0 (bottom edge) and −1.2 (top edge). The black line shows the ionizing spectra of a star-forming galaxy with metallicity Z = 0.017. Vertical lines indicate the ionizing energies of ions of different species (dashed line for hydrogen and continuous lines for the metal transitions considered in this work; gray and green for optical and mid-IR, respectively).