A Massive Yellow Supergiant in the Far Outer Disk of M31: Evidence for in Situ Massive Star Formation beyond the Optical Radius
While massive stars are known to shape galactic ecosystems, their formation has long been assumed to require the high-density environments of inner galactic disks. This paradigm is challenged by mounting evidence of young massive stars in extended galaxy outskirts, yet direct confirmation of in situ...
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IOP Publishing
2025-01-01
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| Series: | The Astronomical Journal |
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| Online Access: | https://doi.org/10.3847/1538-3881/ade68a |
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| author | Pinjian Chen Bingqiu Chen Haibo Yuan Xuan Fang Xiaodian Chen Chao-Wei Tsai Kai Zhang Xiaowei Liu |
| author_facet | Pinjian Chen Bingqiu Chen Haibo Yuan Xuan Fang Xiaodian Chen Chao-Wei Tsai Kai Zhang Xiaowei Liu |
| author_sort | Pinjian Chen |
| collection | DOAJ |
| description | While massive stars are known to shape galactic ecosystems, their formation has long been assumed to require the high-density environments of inner galactic disks. This paradigm is challenged by mounting evidence of young massive stars in extended galaxy outskirts, yet direct confirmation of in situ massive star formation in such extreme low-density environments remains scarce. Here, we present the discovery of LAMOST J0048+4154, a massive yellow supergiant situated at a deprojected galactocentric distance of ∼34 kpc in M31, making it the most distant massive star confirmed in this galaxy. Through spectroscopic and photometric analyses, we classify J0048+4154 as an F5–F8I supergiant with an effective temperature of $635{7}_{-118}^{+121}$ K and a luminosity of ${\mathrm{log}}\,L/{L}_{\odot }=5.0{0}_{-0.06}^{+0.06}$ , corresponding to an ∼18 M _⊙ progenitor and an age of ∼10 Myr. FAST H i observations reveal close spatial and kinematic alignment between the star and a faint H i external arm, suggesting in situ formation in a region of low gas density. The presence of other UV-bright, early-type stars in the vicinity further supports low-level recent star formation in M31’s very outer disk. These findings challenge the prevailing assumption that massive star formation is confined to inner disks or classical star-forming regions and underscore the need to reexamine the role of spiral galaxy outskirts in fueling and sustaining star formation. J0048+4154 thereby expands our understanding of the extent of M31’s young stellar component and exemplifies how outer disks may harbor conditions conducive to forming massive stars despite low-density environments. |
| format | Article |
| id | doaj-art-e9054fae0d7b4824b74717ccedad0cee |
| institution | Kabale University |
| issn | 1538-3881 |
| language | English |
| publishDate | 2025-01-01 |
| publisher | IOP Publishing |
| record_format | Article |
| series | The Astronomical Journal |
| spelling | doaj-art-e9054fae0d7b4824b74717ccedad0cee2025-08-20T03:30:24ZengIOP PublishingThe Astronomical Journal1538-38812025-01-0117028910.3847/1538-3881/ade68aA Massive Yellow Supergiant in the Far Outer Disk of M31: Evidence for in Situ Massive Star Formation beyond the Optical RadiusPinjian Chen0https://orcid.org/0009-0007-5623-2475Bingqiu Chen1https://orcid.org/0000-0003-2472-4903Haibo Yuan2https://orcid.org/0000-0003-2471-2363Xuan Fang3https://orcid.org/0000-0003-1286-2743Xiaodian Chen4https://orcid.org/0000-0001-7084-0484Chao-Wei Tsai5https://orcid.org/0000-0002-9390-9672Kai Zhang6https://orcid.org/0000-0003-0985-6166Xiaowei Liu7https://orcid.org/0000-0003-1295-2909National Astronomical Observatories, Chinese Academy of Sciences , Beijing 100101, People’s Republic of China; School of Astronomy and Space Science, University of the Chinese Academy of Sciences , Beijing 100049, People’s Republic of ChinaSouth-Western Institute for Astronomy Research, Yunnan University , Kunming, Yunnan 650091, People’s Republic of China ; bchen@ynu.edu.cnSchool of Physics and Astronomy, Beijing Normal University , Beijing 100875, People’s Republic of China; Institute for Frontiers in Astronomy and Astrophysics, Beijing Normal University , Beijing 102206, People’s Republic of ChinaNational Astronomical Observatories, Chinese Academy of Sciences , Beijing 100101, People’s Republic of China; School of Astronomy and Space Science, University of the Chinese Academy of Sciences , Beijing 100049, People’s Republic of China; Xinjiang Astronomical Observatory, Chinese Academy of Sciences , 150 Science 1-Street, Urumqi, Xinjiang 830011, People’s Republic of ChinaNational Astronomical Observatories, Chinese Academy of Sciences , Beijing 100101, People’s Republic of China; School of Astronomy and Space Science, University of the Chinese Academy of Sciences , Beijing 100049, People’s Republic of China; Institute for Frontiers in Astronomy and Astrophysics, Beijing Normal University , Beijing 102206, People’s Republic of ChinaNational Astronomical Observatories, Chinese Academy of Sciences , Beijing 100101, People’s Republic of China; School of Astronomy and Space Science, University of the Chinese Academy of Sciences , Beijing 100049, People’s Republic of China; Institute for Frontiers in Astronomy and Astrophysics, Beijing Normal University , Beijing 102206, People’s Republic of ChinaNational Astronomical Observatories, Chinese Academy of Sciences , Beijing 100101, People’s Republic of China; School of Astronomy and Space Science, University of the Chinese Academy of Sciences , Beijing 100049, People’s Republic of ChinaSouth-Western Institute for Astronomy Research, Yunnan University , Kunming, Yunnan 650091, People’s Republic of China ; bchen@ynu.edu.cnWhile massive stars are known to shape galactic ecosystems, their formation has long been assumed to require the high-density environments of inner galactic disks. This paradigm is challenged by mounting evidence of young massive stars in extended galaxy outskirts, yet direct confirmation of in situ massive star formation in such extreme low-density environments remains scarce. Here, we present the discovery of LAMOST J0048+4154, a massive yellow supergiant situated at a deprojected galactocentric distance of ∼34 kpc in M31, making it the most distant massive star confirmed in this galaxy. Through spectroscopic and photometric analyses, we classify J0048+4154 as an F5–F8I supergiant with an effective temperature of $635{7}_{-118}^{+121}$ K and a luminosity of ${\mathrm{log}}\,L/{L}_{\odot }=5.0{0}_{-0.06}^{+0.06}$ , corresponding to an ∼18 M _⊙ progenitor and an age of ∼10 Myr. FAST H i observations reveal close spatial and kinematic alignment between the star and a faint H i external arm, suggesting in situ formation in a region of low gas density. The presence of other UV-bright, early-type stars in the vicinity further supports low-level recent star formation in M31’s very outer disk. These findings challenge the prevailing assumption that massive star formation is confined to inner disks or classical star-forming regions and underscore the need to reexamine the role of spiral galaxy outskirts in fueling and sustaining star formation. J0048+4154 thereby expands our understanding of the extent of M31’s young stellar component and exemplifies how outer disks may harbor conditions conducive to forming massive stars despite low-density environments.https://doi.org/10.3847/1538-3881/ade68aAndromeda galaxyF supergiant starsMassive starsStar formation |
| spellingShingle | Pinjian Chen Bingqiu Chen Haibo Yuan Xuan Fang Xiaodian Chen Chao-Wei Tsai Kai Zhang Xiaowei Liu A Massive Yellow Supergiant in the Far Outer Disk of M31: Evidence for in Situ Massive Star Formation beyond the Optical Radius The Astronomical Journal Andromeda galaxy F supergiant stars Massive stars Star formation |
| title | A Massive Yellow Supergiant in the Far Outer Disk of M31: Evidence for in Situ Massive Star Formation beyond the Optical Radius |
| title_full | A Massive Yellow Supergiant in the Far Outer Disk of M31: Evidence for in Situ Massive Star Formation beyond the Optical Radius |
| title_fullStr | A Massive Yellow Supergiant in the Far Outer Disk of M31: Evidence for in Situ Massive Star Formation beyond the Optical Radius |
| title_full_unstemmed | A Massive Yellow Supergiant in the Far Outer Disk of M31: Evidence for in Situ Massive Star Formation beyond the Optical Radius |
| title_short | A Massive Yellow Supergiant in the Far Outer Disk of M31: Evidence for in Situ Massive Star Formation beyond the Optical Radius |
| title_sort | massive yellow supergiant in the far outer disk of m31 evidence for in situ massive star formation beyond the optical radius |
| topic | Andromeda galaxy F supergiant stars Massive stars Star formation |
| url | https://doi.org/10.3847/1538-3881/ade68a |
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