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Although the 2P3/2-2P1/2 transition of [CII] at 158um is known to be anexcellent tracer of active star formation, we still do not have a completeunderstanding of where within star formation regions the emission originates.Here, we use SOFIA upGREAT observations of [CII] emission toward the HII regioncomplex Sh2-235 (S235) to better understand in detail the origin of [CII]emission. We complement these data with a fully-sampled Green Bank Telescoperadio recombination line map tracing the ionized hydrogen gas. About half ofthe total [CII] emission associated with S235 is spatially coincident withionized hydrogen gas, although spectroscopic analysis shows little evidencethat this emission is coming from the ionized hydrogen volume.Velocity-integrated [CII] intensity is strongly correlated with WISE 12umintensity across the entire complex, indicating that both trace ultra-violetradiation fields. The 22um and radio continuum intensities are only correlatedwith [CII] intensity in the ionized hydrogen portion of the S235 region and thecorrelations between the [CII] and molecular gas tracers are poor across theregion. We find similar results for emission averaged over a sample of externalgalaxies, although the strength of the correlations is weaker. Therefore,although many tracers are correlated with the strength of [CII] emission, onlyWISE 12um emission is correlated on small-scales of the individual HII regionS235 and also has a decent correlation at the scale of entire galaxies. Futurestudies of a larger sample of Galactic HII regions would help to determinewhether these results are truly representative.

The Origin of [CII] 158um Emission toward the HII Region Complex S235