The Origin of [C ii] 158 μm Emission toward the H ii Region Complex S235

• Published in: The Astrophysical journal Vol. 882; no. 1; p. 11
• Main Authors: Anderson, L. D., Makai, Z., Luisi, M., Andersen, M., Russeil, D., Samal, M. R., Schneider, N., Tremblin, P., Zavagno, A., Kirsanova, M. S., Ossenkopf-Okada, V., Sobolev, A. M.
• Format: Journal Article
• Language: English
• Published: Philadelphia IOP Publishing 01.09.2019; American Astronomical Society
• Subjects: Astrophysics; Correlation; Emission analysis; Galaxies; H II regions; Hydrogen; Infrared astronomy; Molecular gases; Sciences of the Universe; Spectroscopic analysis; Star & galaxy formation; Star formation; Tracers; Ultraviolet radiation; Wide-field Infrared Survey Explorer
• ISSN: 0004-637X; 1538-4357
• DOI: 10.3847/1538-4357/ab1c59

Abstract Although the transition of [C ii ] at λ  ≃  158 is known to be an excellent tracer of active star formation, we still do not have a complete understanding of where within star formation regions the emission originates. Here, we use SOFIA upGREAT observations of [C ii ] emission toward the H ii region complex Sh2-235 (S235) to better understand in detail the origin of [C ii ] emission. We complement these data with a fully sampled Green Bank Telescope radio recombination line map tracing the ionized hydrogen gas. About half of the total [C ii ] emission associated with S235 is spatially coincident with ionized hydrogen gas, although spectroscopic analysis shows little evidence that this emission is coming from the ionized hydrogen volume. Velocity-integrated [C ii ] intensity is strongly correlated with Wide-field Infrared Survey Explorer ( WISE ) 12 intensity across the entire complex, indicating that both trace ultraviolet radiation fields. The 22 and radio continuum intensities are only correlated with [C ii ] intensity in the ionized hydrogen portion of the S235 region and the correlations between the [C ii ] and molecular gas tracers are poor across the region. We find similar results for emission averaged over a sample of external galaxies, although the strength of the correlations is weaker. Therefore, although many tracers are correlated with the strength of [C ii ] emission, only WISE 12 emission is correlated on small scales of the individual H ii region S235 and also has a decent correlation at the scale of entire range of galaxies. Future studies of a larger sample of Galactic H ii regions would help to determine whether these results are truly representative.