J. D.T. Smith, Kevin Croxall, Bruce Draine, Ilse De Looze, Karin Sandstrom, Lee Armus, Pedro Beirão, Alberto Bolatto, Mederic Boquien, Bernhard Brandl, Alison Crocker, Daniel A. Dale, Maud Galametz, Brent Groves, George Helou, Rodrigo Herrera-Camus, Leslie Hunt, Robert Kennicutt, Fabian Walter, Mark Wolfire

Research output: Contribution to journalArticlepeer-review

81 Scopus citations


We present [C ii] 158 μm measurements from over 15,000 resolved regions within 54 nearby galaxies of the Kingfish program to investigate the so-called [C ii] "line-cooling deficit" long known to occur in galaxies with different luminosities. The [C ii]/TIR ratio ranges from above 1% to below 0.1% in the sample, with a mean value of 0.48 ± 0.21%. We find that the surface density of 24 μm emission dominates this trend, with [C ii]/TIR dropping as vIv (24 μm)increases. Deviations from this overall decline are correlated with changes in the gas-phase metal abundance, with higher metallicity associated with deeper deficits at a fixed surface brightness. We supplement the local sample with resolved [C ii] measurements from nearby luminous infrared galaxies and high-redshift sources from z = 1.8-6.4, and find that star formation rate density drives a continuous trend of deepening [C ii] deficit across six orders of magnitude in ΣSFR. The tightness of this correlation suggests that an approximate can be estimated directly from global measurements of [C ii]/TIR, and a relation is provided to do so. Several low-luminosity active galactic nucleus (AGN) hosts in the sample show additional and significant central suppression of [C ii]/TIR, but these deficit enhancements occur not in those AGNs with the highest X-ray luminosities, but instead those with the highest central starlight intensities. Taken together, these results demonstrate that the [C ii] line-cooling line deficit in galaxies likely arises from local physical phenomena in interstellar gas.

Original languageEnglish (US)
Article number5
JournalAstrophysical Journal
Issue number1
StatePublished - Jan 1 2017

All Science Journal Classification (ASJC) codes

  • Astronomy and Astrophysics
  • Space and Planetary Science


  • dust, extinction
  • galaxies: ISM
  • infrared: galaxies
  • techniques: spectroscopic


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