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The Origins of [C II] Emission in Local Star-forming Galaxies

Author(s): Croxall, KV; Smith, JD; Pellegrini, Eric W.; Groves, B; Bolatto, A; et al

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Abstract: The [C II] 158 mu m fine-structure line is the brightest emission line observed in local star-forming galaxies. As a major coolant of the gas-phase interstellar medium, [C II] balances the heating, including that due to far-ultraviolet photons, which heat the gas via the photoelectric effect. However, the origin of [C II] emission remains unclear because C+ can be found in multiple phases of the interstellar medium. Here we measure the fractions of [C II] emission originating in the ionized and neutral gas phases of a sample of nearby galaxies. We use the [N II] 205 mu m fine-structure line to trace the ionized medium, thereby eliminating the strong density dependence that exists in the ratio of [C II]/[N II] 122 mu m. Using the FIR [C II] and [N II] emission detected by the KINGFISH (Key Insights on Nearby Galaxies: a Far-Infrared Survey with Herschel) and Beyond the Peak Herschel programs, we show that 60%-80% of [C II] emission originates from neutral gas. We find that the fraction of [C II] originating in the neutral medium has a weak dependence on dust temperature and the surface density of star formation, and has a stronger dependence on the gas-phase metallicity. In metal-rich environments, the relatively cooler ionized gas makes substantially larger contributions to total [C II] emission than at low abundance, contrary to prior expectations. Approximate calibrations of this metallicity trend are provided.
Publication Date: 20-Aug-2017
Electronic Publication Date: 16-Aug-2017
Citation: Croxall, KV, Smith, JD, Pellegrini, E, Groves, B, Bolatto, A, Herrera-Camus, R, Sandstrom, KM, Draine, B, Wolfire, MG, Armus, L, Boquien, M, Brandl, B, Dale, D, Galametz, M, Hunt, L, Kennicutt, R, Kreckel, K, Rigopoulou, D, van der Werf, P, Wilson, C. (2017). The Origins of [C II] Emission in Local Star-forming Galaxies. ASTROPHYSICAL JOURNAL, 845 (10.3847/1538-4357/aa8035
DOI: doi:10.3847/1538-4357/aa8035
ISSN: 0004-637X
EISSN: 1538-4357
Type of Material: Journal Article
Journal/Proceeding Title: ASTROPHYSICAL JOURNAL
Version: Final published version. Article is made available in OAR by the publisher's permission or policy.
Notes: Supplementary data available at , , and

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