1. The Origins of [C II] Emission in Local Star-forming Galaxies
- Author
-
Alberto D. Bolatto, Bruce T. Draine, P. van der Werf, Karin Sandstrom, Kevin V. Croxall, Rodrigo Herrera-Camus, Dimitra Rigopoulou, Mark G. Wolfire, J. D. Smith, Médéric Boquien, Daniel A. Dale, Maud Galametz, Kathryn Kreckel, Robert C. Kennicutt, Brent Groves, Christine D. Wilson, Eric W. Pellegrini, Lee Armus, Leslie K. Hunt, Bernhard R. Brandl, Croxall, KV [0000-0002-5258-7224], Smith, JD [0000-0003-1545-5078], Groves, B [0000-0002-9768-0246], Bolatto, A [0000-0002-5480-5686], Herrera-Camus, R [0000-0002-2775-0595], Sandstrom, KM [0000-0002-4378-8534], Draine, B [0000-0002-0846-936X], Wolfire, MG [0000-0003-0030-9510], Dale, D [0000-0002-5782-9093], Galametz, M [0000-0002-0283-8689], Hunt, L [0000-0001-9162-2371], Kreckel, K [0000-0001-6551-3091], Werf, PVD [0000-0001-5434-5942], Apollo - University of Cambridge Repository, and USA
- Subjects
Infrared ,Metallicity ,FOS: Physical sciences ,Astrophysics ,Astrophysics::Cosmology and Extragalactic Astrophysics ,Computer Science::Computational Geometry ,01 natural sciences ,0103 physical sciences ,Astrophysics::Solar and Stellar Astrophysics ,Emission spectrum ,010303 astronomy & astrophysics ,Astrophysics::Galaxy Astrophysics ,Line (formation) ,Cosmic dust ,Physics ,010308 nuclear & particles physics ,Star formation ,Astronomy and Astrophysics ,Astrophysics - Astrophysics of Galaxies ,Galaxy ,ISM: lines and bands ,Interstellar medium ,Space and Planetary Science ,Astrophysics of Galaxies (astro-ph.GA) ,Astrophysics::Earth and Planetary Astrophysics ,galaxies: ISM - Abstract
The [CII] 158um fine-structure line is the brightest emission line observed in local star-forming galaxies. As a major coolant of the gas-phase interstellar medium, [CII] balances the heating, including that due to far-ultraviolet photons, which heat the gas via the photoelectric effect. However, the origin of [CII] emission remains unclear, because C+ can be found in multiple phases of the interstellar medium. Here we measure the fractions of [CII] emission originating in the ionized and neutral gas phases of a sample of nearby galaxies. We use the [NII] 205um fine-structure line to trace the ionized medium, thereby eliminating the strong density dependence that exists in the ratio of [CII]/[NII] 122um. Using the FIR [CII] and [NII] emission detected by the KINGFISH and Beyond the Peak Herschel programs, we show that 60-80% of [CII] emission originates from neutral gas. We find that the fraction of [CII] originating in the neutral medium has a weak dependence on dust temperature and the surface density of star formation, and a stronger dependence on the gas-phase metallicity. In metal-rich environments, the relatively cooler ionized gas makes substantially larger contributions to total [CII] emission than at low abundance, contrary to prior expectations. Approximate calibrations of this metallicity trend are provided., Comment: 8 pages, accepted for publication in ApJ
- Published
- 2017