[CI](1-0) and [CI](2-1) in resolved local galaxies

Abstract

We present resolved [CI] 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 $J_{\mathrm{up}}=1$ to 7 to interpret what phase of the interstellar medium the [CI] lines trace within typical local galaxies. A tight, linear relation is found between the intensities of the CO(4-3) and [CI](2-1) lines; we hypothesize this is due to the similar upper level temperature of these two lines. We modeled the [CI] and CO line emission using large velocity gradient models combined with an empirical template. According to this modeling, the [CI](1-0) line is clearly dominated by the low-excitation component. We determine [CI] to molecular mass conversion factors for both the [CI](1-0) and [CI](2-1) lines, with mean values of ${\alpha }_{[\mathrm{CI}](1-0)}=7.3$ M${}_{\mathrm{sun}}$ K${}^{-1}$ km${}^{-1}$ s pc${}^{-2}$ and ${\alpha }_{[\mathrm{CI}](2-1)}=34$ M${}_{\mathrm{sun}}$ 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 ${\alpha }_{[\mathrm{CI}](1-0)}$ to ${\alpha }_{\mathrm{CO}}$ (derived using the CO(2-1) line) suggests that [CI](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 ${\alpha }_{[\mathrm{CI}](2-1)}$ and the tight relation found between [CI](2-1) and CO(4-3) suggest that much of the [CI](2-1) emission may originate in warmer molecular gas.

15 pages, 10 figures, published in ApJ

References in corpus (6)

• The Spatially Resolved [CII] Cooling Line Deficit in Galaxies
• Modelling [CI] emission from turbulent molecular clouds
• A Survey of the Molecular ISM Properties of Nearby Galaxies using the Herschel FTS
• Neutral carbon and CO in 76 (U)LIRGs and starburst galaxy centers A method to determine molecular gas properties in luminous galaxies
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• Probing the cold and warm molecular gas in the Whirlpool Galaxy: Herschel SPIRE-FTS Observations of the central region of M51 (NGC 5194)

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• ALMA Observations of Multiple-CO and C Lines Toward the Active Galactic Nucleus of NGC 7469: X-Ray-dominated Region Caught in the Act
• Cold gas disks in main-sequence galaxies at cosmic noon: Low turbulence, flat rotation curves, and disk-halo degeneracy
• Direct measurement of the [CI] luminosity to molecular gas mass conversion factor in high-redshift star-forming galaxies
• Discovery of a [CI]-faint, CO-bright Galaxy: ALMA Observations of the Merging Galaxy NGC 6052
• Gas and Star Formation from HD and Dust Emission in a Strongly Lensed Galaxy
• Atomic Carbon [CI]${(}^3{P}_1{-}^3{P}_0)$ Mapping of the Nearby Galaxy M83