Neutral Atomic and Molecular Clouds and Star Formation in the Outer Carina Arm
We present a comprehensive investigation of H i (super)clouds, molecular clouds (MCs), and star formation in the Carina spiral arm of the outer Galaxy. Utilizing HI4PI and CfA CO survey data, we identify H i clouds and MCs based on the ( l , v _LSR ) locations of the Carina arm. We analyzed 26 H i c...
| Main Authors: | , , , |
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| Format: | Article |
| Language: | English |
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IOP Publishing
2023-01-01
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| Series: | The Astrophysical Journal |
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| Online Access: | https://doi.org/10.3847/1538-4357/acebda |
| _version_ | 1797682300605956096 |
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| author | Geumsook Park Bon-Chul Koo Kee-Tae Kim Bruce Elmegreen |
| author_facet | Geumsook Park Bon-Chul Koo Kee-Tae Kim Bruce Elmegreen |
| author_sort | Geumsook Park |
| collection | DOAJ |
| description | We present a comprehensive investigation of H i (super)clouds, molecular clouds (MCs), and star formation in the Carina spiral arm of the outer Galaxy. Utilizing HI4PI and CfA CO survey data, we identify H i clouds and MCs based on the ( l , v _LSR ) locations of the Carina arm. We analyzed 26 H i clouds and 48 MCs. Most of the identified H i clouds are superclouds, with masses exceeding 10 ^6 M _⊙ . We find that 15 of these superclouds have associated MC(s) with M _H I ≳ 10 ^6 M _⊙ and ${{\rm{\Sigma }}}_{{\rm{H}}\,{\rm\small{I}}+{{\rm{H}}}_{2}}\gtrsim $ 50 M _⊙ pc ^−2 . Our virial equilibrium analysis suggests that these CO-bright H i clouds are gravitationally bound or marginally bound. We report an anticorrelation between molecular mass fractions and Galactocentric distances, and a correlation with total gas surface densities. Nine CO-bright H i superclouds are associated with H ii regions, indicating ongoing star formation. We confirm the regular spacing of H i superclouds along the spiral arm, which is likely due to some underlying physical process, such as gravitational instabilities. We observe a strong spatial correlation between H ii regions and MCs, with some offsets between MCs and local H i column density peaks. Our study reveals that, in the context of H i superclouds, the star formation rate surface density is independent of H i and total gas surface densities but positively correlates with molecular gas surface density. This finding is consistent with both extragalactic studies of the resolved Kennicutt–Schmidt relation and local giant molecular clouds study of Lada et al. (2013), emphasizing the crucial role of molecular gas in regulating star formation processes. |
| first_indexed | 2024-03-11T23:57:45Z |
| format | Article |
| id | doaj.art-ff4fb25a603449e3b8e3287694dd9081 |
| institution | Directory Open Access Journal |
| issn | 1538-4357 |
| language | English |
| last_indexed | 2024-03-11T23:57:45Z |
| publishDate | 2023-01-01 |
| publisher | IOP Publishing |
| record_format | Article |
| series | The Astrophysical Journal |
| spelling | doaj.art-ff4fb25a603449e3b8e3287694dd90812023-09-18T10:29:42ZengIOP PublishingThe Astrophysical Journal1538-43572023-01-0195515910.3847/1538-4357/acebdaNeutral Atomic and Molecular Clouds and Star Formation in the Outer Carina ArmGeumsook Park0https://orcid.org/0000-0001-8467-3736Bon-Chul Koo1https://orcid.org/0000-0002-2755-1879Kee-Tae Kim2https://orcid.org/0000-0003-2412-7092Bruce Elmegreen3https://orcid.org/0000-0002-1723-6330Korea Astronomy and Space Science Institute , 776 Daedeokdae-ro, Yuseong-gu, Daejeon 34055, Republic of Korea; Research Institute of Natural Sciences, Chungnam National University 99 Daehak-ro , Yuseong-gu, Daejeon 34134, Republic of KoreaDepartment of Physics and Astronomy, Seoul National University , Seoul 08861, Republic of Korea; Research Institute of Basic Sciences, Seoul National University , Seoul 08826, Republic of KoreaKorea Astronomy and Space Science Institute , 776 Daedeokdae-ro, Yuseong-gu, Daejeon 34055, Republic of Korea; University of Science and Technology , Korea (UST), 217 Gajeong-ro, Yuseong-gu, Daejeon 34113, Republic of KoreaIBM Thomas J. Watson Research Center , Yorktown Heights, NY 10598, USAWe present a comprehensive investigation of H i (super)clouds, molecular clouds (MCs), and star formation in the Carina spiral arm of the outer Galaxy. Utilizing HI4PI and CfA CO survey data, we identify H i clouds and MCs based on the ( l , v _LSR ) locations of the Carina arm. We analyzed 26 H i clouds and 48 MCs. Most of the identified H i clouds are superclouds, with masses exceeding 10 ^6 M _⊙ . We find that 15 of these superclouds have associated MC(s) with M _H I ≳ 10 ^6 M _⊙ and ${{\rm{\Sigma }}}_{{\rm{H}}\,{\rm\small{I}}+{{\rm{H}}}_{2}}\gtrsim $ 50 M _⊙ pc ^−2 . Our virial equilibrium analysis suggests that these CO-bright H i clouds are gravitationally bound or marginally bound. We report an anticorrelation between molecular mass fractions and Galactocentric distances, and a correlation with total gas surface densities. Nine CO-bright H i superclouds are associated with H ii regions, indicating ongoing star formation. We confirm the regular spacing of H i superclouds along the spiral arm, which is likely due to some underlying physical process, such as gravitational instabilities. We observe a strong spatial correlation between H ii regions and MCs, with some offsets between MCs and local H i column density peaks. Our study reveals that, in the context of H i superclouds, the star formation rate surface density is independent of H i and total gas surface densities but positively correlates with molecular gas surface density. This finding is consistent with both extragalactic studies of the resolved Kennicutt–Schmidt relation and local giant molecular clouds study of Lada et al. (2013), emphasizing the crucial role of molecular gas in regulating star formation processes.https://doi.org/10.3847/1538-4357/acebdaInterstellar clouds |
| spellingShingle | Geumsook Park Bon-Chul Koo Kee-Tae Kim Bruce Elmegreen Neutral Atomic and Molecular Clouds and Star Formation in the Outer Carina Arm The Astrophysical Journal Interstellar clouds |
| title | Neutral Atomic and Molecular Clouds and Star Formation in the Outer Carina Arm |
| title_full | Neutral Atomic and Molecular Clouds and Star Formation in the Outer Carina Arm |
| title_fullStr | Neutral Atomic and Molecular Clouds and Star Formation in the Outer Carina Arm |
| title_full_unstemmed | Neutral Atomic and Molecular Clouds and Star Formation in the Outer Carina Arm |
| title_short | Neutral Atomic and Molecular Clouds and Star Formation in the Outer Carina Arm |
| title_sort | neutral atomic and molecular clouds and star formation in the outer carina arm |
| topic | Interstellar clouds |
| url | https://doi.org/10.3847/1538-4357/acebda |
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