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

K. V. Croxall; J. D. Smith; E. Pellegrini; B. Groves; A. Bolatto; R. Herrera-Camus; K. M. Sandstrom; B. Draine; M. G. Wolfire; L. Armus; M. Boquien; B. Brandl; D. Dale; M. Galametz; L. Hunt; R. Kennicutt; K. Kreckel; D. Rigopoulou; P. Van Der Werf; C. Wilson

doi:10.3847/1538-4357/aa8035

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

K. V. Croxall, J. D. Smith, E. Pellegrini, B. Groves, A. Bolatto, R. Herrera-Camus, K. M. Sandstrom, B. Draine, M. G. Wolfire, L. Armus, M. Boquien, B. Brandl, D. Dale, M. Galametz, L. Hunt, R. Kennicutt, K. Kreckel, D. Rigopoulou, P. Van Der Werf, C. Wilson

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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.

Original language	English
Article number	96
Journal	Astrophysical Journal
Volume	845
Issue number	2
DOIs	https://doi.org/10.3847/1538-4357/aa8035
Publication status	Published - 20 Aug 2017

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Croxall, K. V., Smith, J. D., Pellegrini, E., Groves, B., Bolatto, A., Herrera-Camus, R., Sandstrom, K. M., Draine, B., Wolfire, M. G., Armus, L., Boquien, M., Brandl, B., Dale, D., Galametz, M., Hunt, L., Kennicutt, R., Kreckel, K., Rigopoulou, D., Werf, P. V. D., & Wilson, C. (2017). The Origins of [C II] Emission in Local Star-forming Galaxies. Astrophysical Journal, 845(2), Article 96. https://doi.org/10.3847/1538-4357/aa8035

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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",

year = "2017",

month = aug,

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doi = "10.3847/1538-4357/aa8035",

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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, Werf, PVD & Wilson, C 2017, 'The Origins of [C II] Emission in Local Star-forming Galaxies', Astrophysical Journal, vol. 845, no. 2, 96. https://doi.org/10.3847/1538-4357/aa8035

TY - JOUR

T1 - The Origins of [C II] Emission in Local Star-forming Galaxies

AU - Croxall, K. V.

AU - Smith, J. D.

AU - Pellegrini, E.

AU - Groves, B.

AU - Bolatto, A.

AU - Herrera-Camus, R.

AU - Sandstrom, K. M.

AU - Draine, B.

AU - Wolfire, M. G.

AU - Armus, L.

AU - Boquien, M.

AU - Brandl, B.

AU - Dale, D.

AU - Galametz, M.

AU - Hunt, L.

AU - Kennicutt, R.

AU - Kreckel, K.

AU - Rigopoulou, D.

AU - Werf, P. Van Der

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 - ISM: lines and bands

KW - galaxies: ISM

UR - http://www.scopus.com/inward/record.url?scp=85028757333&partnerID=8YFLogxK

U2 - 10.3847/1538-4357/aa8035

DO - 10.3847/1538-4357/aa8035

M3 - Article

SN - 0004-637X

VL - 845

JO - Astrophysical Journal

JF - Astrophysical Journal

IS - 2

M1 - 96

ER -

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

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