[C i](1–0) and [C i](2–1) in Resolved Local Galaxies

Alison F. Crocker, Eric Pellegrini, J. D.T. Smith, Bruce T. Draine, Christine D. Wilson, Mark Wolfire, Lee Armus, Elias Brinks, Daniel A. Dale, Brent Groves, Rodrigo Herrera-Camus, Leslie K. Hunt, Robert C. Kennicutt, Eric J. Murphy, Karin Sandstrom, Eva Schinnerer, Dimitra Rigopoulou, Erik Rosolowsky, Paul Van Der Werf

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21 Scopus citations


We present resolved [C i] line intensities of 18 nearby galaxies observed with the SPIRE FTS spectrometer on the Herschel Space Observatory. We use these data along with resolved CO line intensities from J up = 1 to 7 to interpret what phase of the interstellar medium the [C i] lines trace within typical local galaxies. A tight, linear relation is found between the intensities of the CO(4-3) and [C i](2-1) lines; we hypothesize this is due to the similar upper level temperature of these two lines. We modeled the [C i] and CO line emission using large-velocity gradient models combined with an empirical template. According to this modeling, the [C i](1-0) line is clearly dominated by the low-excitation component. We determine [C i] to molecular mass conversion factors for both the [C i](1-0) and [C i](2-1) lines, with mean values of α [C i](1-0) = 7.3 M o K-1 km-1 s pc-2 and α [C i](2-1) = 34 M o K-1 km-1 s pc-2 with logarithmic root-mean-square spreads of 0.20 and 0.32 dex, respectively. The similar spread of α [C I](1-0) to αCO (derived using the CO(2-1) line) suggests that [C i](1-0) may be just as good a tracer of cold molecular gas as CO(2-1) in galaxies of this type. On the other hand, the wider spread of α [C i](2-1) and the tight relation found between [C i](2-1) and CO(4-3) suggest that much of the [C i](2-1) emission may originate in warmer molecular gas.

Original languageEnglish (US)
Article number105
JournalAstrophysical Journal
Issue number1
StatePublished - Dec 10 2019

All Science Journal Classification (ASJC) codes

  • Astronomy and Astrophysics
  • Space and Planetary Science


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