Relative contributions of PDRs and H II regions to [Si II], [Fe II], and [C II] fine‐structure emission. Shown are our standard model results for ﹩\Phi _{i}=10^{49}﹩ (solid lines) and 10⁵¹ s⁻¹ (dashed lines). In the [C II] panel, the triangle shows the result for the standard star cluster but for an age of only 10⁶ yr. The square shows the result for the case where the cluster spectrum is a blackbody. See § 3.2 for details.