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

Journal article (2017)

Authors

Kevin Croxall Illumination Works LLC, Ohio State University, Max-Planck-Institut für Astronomie
J. D T Smith University of Toledo, Max-Planck-Institut für Astronomie
M. Boquien Universidad de Antofagasta
B.R. Brandl Astrodynamics & Space Missions - Aerospace Engineering , Universiteit Leiden
Daniel A. Dale University of Wyoming
Maud Galametz European Southern Observatory, ENS-PSL Research University & CNRS
L. K. Hunt INAF-Osservatorio Astrofisico di Arcetri
R. C. Kennicutt University of Cambridge
K. Kreckel Max-Planck-Institut für Astronomie
Dimitra Rigopoulou University of Oxford
Paul van der werf Universiteit Leiden
C Wilson McMaster University
E. Pellegrini University of Toledo, University of Heidelberg
Brent Groves Australian National University
A. Bolatto University of Maryland
Rodrigo Herrera-Camus Max Planck Institute for Extraterrestrial Physics Garching
K. M. Sandstrom University of California
Bruce Draine Princeton University
Mark Wolfire University of Maryland
Lee Armus Spitzer Science Center
Research Group
Astrodynamics & Space Missions (Aerospace Engineering) (TU Delft)
Copyright: © 2017 K. V. Croxall, J. D T Smith, E. Pellegrini, Brent Groves, Alberto Bolatto, Rodrigo Herrera-Camus, K. M. Sandstrom, Bruce Draine, M. G. Wolfire, Lee Armus, Mederic Boquien, B.R. Brandl, Daniel A. Dale, Maud Galametz, L. K. Hunt, R. C. Kennicutt, K. Kreckel, D. Rigopoulou, p van der werf, C Wilson
DOI
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https://doi.org/10.3847/1538-4357/aa8035
Galaxies: ISM ISM: lines and bands
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Published Date

20-08-2017

Language

English

Reuse Rights

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Faculty

Aerospace Engineering

Department

Space Engineering

Research Group

Astrodynamics & Space Missions

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.

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