C I and CO in nearby spiral galaxies: I. Line ratio and abundance variations at ∼200 pc scales
We present new neutral atomic carbon [C I] (<sup>3<sup/>P<sub>1<sub/> → <sup>3<sup/>P<sub>0<sub/>) mapping observations within the inner ∼7 kpc and ∼4 kpc of the disks of NGC 3627 and NGC 4321 at a spatial resolution of 190 pc and 270 pc, respectively,...
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| Main Authors: | , , , , , , , , , , , , , , , , , , , , , , , , , , , |
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| Format: | Article (Journal) |
| Language: | English |
| Published: |
April 2023
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| In: |
Astronomy and astrophysics
Year: 2023, Volume: 672, Pages: 1-22 |
| ISSN: | 1432-0746 |
| DOI: | 10.1051/0004-6361/202244564 |
| Online Access: | Verlag, kostenfrei, Volltext: https://doi.org/10.1051/0004-6361/202244564 Verlag, kostenfrei, Volltext: https://www.aanda.org/articles/aa/abs/2023/04/aa44564-22/aa44564-22.html 
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| Author Notes: | Daizhong Liu, Eva Schinnerer, Toshiki Saito, Erik Rosolowsky, Adam Leroy, Antonio Usero, Karin Sandstrom, Ralf S. Klessen, Simon C.O. Glover, Yiping Ao, Ivana Bešlić, Frank Bigiel, Yixian Cao, Jérémy Chastenet, Mélanie Chevance, Daniel A. Dale, Yu Gao, Annie Hughes, Kathryn Kreckel, J.M. Diederik Kruijssen, Hsi-An Pan, Jérôme Pety, Dragan Salak, Francesco Santoro, Andreas Schruba, Jiayi Sun, Yu-Hsuan Teng, and Thomas Williams |
| Summary: | We present new neutral atomic carbon [C I] (<sup>3<sup/>P<sub>1<sub/> → <sup>3<sup/>P<sub>0<sub/>) mapping observations within the inner ∼7 kpc and ∼4 kpc of the disks of NGC 3627 and NGC 4321 at a spatial resolution of 190 pc and 270 pc, respectively, using the Atacama Large Millimeter/Submillimeter Array (ALMA) Atacama Compact Array (ACA). We combine these with the CO(2−1) data from PHANGS-ALMA, and literature [C I] and CO data for two other starburst and/or active galactic nucleus (AGN) galaxies (NGC 1808, NGC 7469) with the aim of studying: (a) the spatial distributions of C I and CO emission; (b) the observed line ratio <i>R<i/><sub>C I/CO<sub/> = <i>I<i/><sub>[<sub>C I](1−0<sub/>)<sub/>/<i>I<i/><sub>CO(2−1<sub/>) as a function of various galactic properties; and (c) the abundance ratio of [C I/CO]. We find excellent spatial correspondence between C I and CO emission and nearly uniform <i>R<i/><sub>C I/CO<sub/> ∼ 0.1 across the majority of the star-forming disks of NGC 3627 and NGC 4321. However, <i>R<i/><sub>C I/CO<sub/> strongly varies from ∼0.05 at the center of NGC 4321 to > 0.2 − 0.5 in NGC 1808’s starbursting center and NGC 7469’s center with an X-ray-luminous AGN. Meanwhile, <i>R<i/><sub>C I/CO<sub/> does not obviously vary with ⟨<i>U<i/>⟩, which is in line with predictions from photodissociation-dominated region (PDR) models. We also find a mildly decreasing <i>R<i/><sub>C I/CO<sub/> value with an increasing metallicity over 0.7 − 0.85 <i>Z<i/><sub>⊙<sub/>, which is consistent with the literature. Assuming various typical interstellar medium (ISM) conditions representing giant molecular clouds, active star-forming regions, and strong starbursting environments, we calculated the (non)local-thermodynamic-equilibrium radiative transfer and estimated the [C I/CO] abundance ratio to be ∼0.1 across the disks of NGC 3627 and NGC 4321, similar to previous large-scale findings in Galactic studies. However, this abundance ratio likely experiences a substantial increase, up to ∼1 and ≳1 − 5 in NGC 1808’s starburst and NGC 7469’s strong AGN environments, respectively. This result is in line with the expectations for cosmic-ray dominated region (CRDR) and X-ray dominated region (XDR) chemistry. Finally, we do not find robust evidence for a generally CO-dark-and-C I-bright gas in the disk areas we probed. |
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| Item Description: | Online veröffentlicht: 27. März 2023 Gesehen am 08.08.2023 |
| Physical Description: | Online Resource |
| ISSN: | 1432-0746 |
| DOI: | 10.1051/0004-6361/202244564 |