TY - JOUR
T1 - The Origins of [C II] Emission in Local Star-forming Galaxies
AU - Croxall, K. V.
AU - Smith, J. D T
AU - Pellegrini, E.
AU - Groves, Brent
AU - Bolatto, Alberto
AU - Herrera-Camus, Rodrigo
AU - Sandstrom, K. M.
AU - Draine, Bruce
AU - Wolfire, M. G.
AU - Armus, Lee
AU - Boquien, Mederic
AU - Brandl, B.
AU - Dale, Daniel A.
AU - Galametz, Maud
AU - Hunt, L. K.
AU - Kennicutt, R. C.
AU - Kreckel, K.
AU - Rigopoulou, D.
AU - van der werf, p
AU - Wilson, C
PY - 2017/8/20
Y1 - 2017/8/20
N2 - 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.
AB - 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.
KW - galaxies: ISM
KW - ISM: lines and bands
UR - http://www.scopus.com/inward/record.url?scp=85028757333&partnerID=8YFLogxK
UR - http://resolver.tudelft.nl/uuid:5627de75-4675-4bc7-9c77-1b928541239e
U2 - 10.3847/1538-4357/aa8035
DO - 10.3847/1538-4357/aa8035
M3 - Article
AN - SCOPUS:85028757333
SN - 0004-637X
VL - 845
JO - The Astrophysical Journal: an international review of astronomy and astronomical physics
JF - The Astrophysical Journal: an international review of astronomy and astronomical physics
IS - 2
M1 - 96
ER -