The H+ region contribution to [C II] 158-μm emission

Abstract

The [C ii] line is an important emission-line diagnostic in photodissociation regions (PDRs), but this emission line can also emerge from ionized gas. This work calculates the contribution of [C ii] emission from ionized gas over a wide range of parameter space by considering the simplified case of an H+ region and PDR in pressure equilibrium. Additionally, these calculations also predict the strong correlation observed between [N ii] emission and [C ii] discussed by previous authors. Overall, the results of these calculations have wide-ranging applications to the interpretation of [C ii] emission in astrophysical environments. © 2006 RAS.