@article{3ee188921e8e457e887d19dbd1055dcd,
title = "The Origins of [C II] Emission in Local Star-forming Galaxies",
abstract = "The [C ii] 158 μm 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 μm 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 μm. 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.",
keywords = "ISM: lines and bands, galaxies: ISM",
author = "Croxall, {K. V.} and Smith, {J. D.} and E. Pellegrini and B. Groves and A. Bolatto and R. Herrera-Camus and Sandstrom, {K. M.} and B. Draine and Wolfire, {M. G.} and L. Armus and M. Boquien and B. Brandl and D. Dale and M. Galametz and L. Hunt and R. Kennicutt and K. Kreckel and D. Rigopoulou and Werf, {P. Van Der} and C. Wilson",
note = "Funding Information: K.V.C. would like to thank T. Diaz-Santos, G. Accurso, R. Pogge, and P. Goldsmith for their useful discussions regarding this work. K.V.C. acknowledges support from the Deutsche For-schungsgemeinschaft Priority Program ISM-SPP 1573 and the MPIA, and thanks the KINGFISH & BTP teams for their support. J.D.S. acknowledges visiting support from the Alexander von Humboldt Foundation and the MPIA. B.G. acknowledges the support of the Australian Research Council via a Future Fellowship (FT140101202). A.D.B. acknowledges partial support from NSF-AST0955836 and 1412419. B.T.D. acknowledges partial support from NSF-AST1408723. M.B. was supported by MINEDUC-UA project, code ANT 1655. Beyond the Peak research has been supported by a NASA/JPL grant (RSA 1427378). HIPE is a joint development by the Herschel Science Ground Segment Consortium, consisting of ESA, the NASA Herschel Science Center, and the HIFI, PACS, and SPIRE consortia. This work is based on observations made with Herschel, a ESA Cornerstone Mission with significant participation by NASA. Support for this work was provided by NASA through an award issued by JPL/Caltech. This research has made use of the NASA/IPAC Extragalactic Database which is operated by JPL/Caltech, under contract with NASA. Publisher Copyright: {\textcopyright} 2017. The American Astronomical Society. All rights reserved..",
year = "2017",
month = aug,
day = "20",
doi = "10.3847/1538-4357/aa8035",
language = "English (US)",
volume = "845",
journal = "Astrophysical Journal",
issn = "0004-637X",
publisher = "IOP Publishing Ltd.",
number = "2",
}