[CI](1-0) and [CI](2-1) in resolved local galaxies. (arXiv:2001.05047v1 [astro-ph.GA])

[CI](1-0) and [CI](2-1) in resolved local galaxies. (arXiv:2001.05047v1 [astro-ph.GA])
<a href="http://arxiv.org/find/astro-ph/1/au:+Crocker_A/0/1/0/all/0/1">Alison F. Crocker</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Pellegrini_E/0/1/0/all/0/1">Eric Pellegrini</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Smith_J/0/1/0/all/0/1">J.-D. T. Smith</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Draine_B/0/1/0/all/0/1">Bruce T. Draine</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Wilson_C/0/1/0/all/0/1">Christine D. Wilson</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Wolfire_M/0/1/0/all/0/1">Mark Wolfire</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Armus_L/0/1/0/all/0/1">Lee Armus</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Brinks_E/0/1/0/all/0/1">Elias Brinks</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Dale_D/0/1/0/all/0/1">Daniel A. Dale</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Groves_B/0/1/0/all/0/1">Brent Groves</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Herrera_Camus_R/0/1/0/all/0/1">Rodrigo Herrera-Camus</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Hunt_L/0/1/0/all/0/1">Leslie K. Hunt</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Kennicutt_R/0/1/0/all/0/1">Robert C. Kennicutt</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Murphy_E/0/1/0/all/0/1">Eric J. Murphy</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Sandstrom_K/0/1/0/all/0/1">Karin Sandstrom</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Schinnerer_E/0/1/0/all/0/1">Eva Schinnerer</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Rigopoulou_D/0/1/0/all/0/1">Dimitra Rigopoulou</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Rosolowsky_E/0/1/0/all/0/1">Erik Rosolowsky</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Werf_P/0/1/0/all/0/1">Paul van der Werf</a>

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.

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.

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