Potential Nitrogen Enrichment via Direct-Collapse Wolf-Rayet Stars in a $z=4.7$ Star-Forming Galaxy
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| Formato: | Preprint |
| Publicado: |
2025
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| author | Zhang, Yechi Morishita, Takahiro Stiavelli, Massimo |
| author_facet | Zhang, Yechi Morishita, Takahiro Stiavelli, Massimo |
| contents | We present analyses of a nitrogen-enriched star-forming galaxy, ID60001, at $z=4.6928$ based on JWST/NIRSpec MSA spectroscopy and NIRCam photometry. From rest-frame optical emission lines we derive the nitrogen-to-oxygen (N/O) abundance ratio of ID60001 to be $\log({\rm N/O})=-0.76_{-0.03}^{+0.03}$ ($[{\rm N/O}]=0.10_{-0.03}^{+0.03}$), which is significantly elevated at the corresponding metallicity $12+\log({\rm O/H})=7.75_{-0.01}^{+0.01}$ ($Z/Z_\odot = 0.12$) compared to local counterparts. We discuss possible scenarios for elevated N/O abundance in ID60001, including pristine gas inflow, Wolf-Rayet (WR) stars, and Oxygen depletion by Type II supernova winds. Based on the moderately broadened He{\sc ii}$λ$4686 emission line, galaxy morphology, and star-formation history, we conclude that the elevated N/O abundance of ID60001 is likely originated from massive ($>25\,M_\odot$) WR stars that directly collapse into a black hole. We also stress the importance of reliable electron density measurements when deriving N/O abundance with rest-frame optical emission lines. |
| format | Preprint |
| id |
arxiv_https___arxiv_org_abs_2502_04817 |
| institution | arXiv |
| publishDate | 2025 |
| record_format | arxiv |
| spellingShingle | Potential Nitrogen Enrichment via Direct-Collapse Wolf-Rayet Stars in a $z=4.7$ Star-Forming Galaxy Zhang, Yechi Morishita, Takahiro Stiavelli, Massimo Astrophysics of Galaxies We present analyses of a nitrogen-enriched star-forming galaxy, ID60001, at $z=4.6928$ based on JWST/NIRSpec MSA spectroscopy and NIRCam photometry. From rest-frame optical emission lines we derive the nitrogen-to-oxygen (N/O) abundance ratio of ID60001 to be $\log({\rm N/O})=-0.76_{-0.03}^{+0.03}$ ($[{\rm N/O}]=0.10_{-0.03}^{+0.03}$), which is significantly elevated at the corresponding metallicity $12+\log({\rm O/H})=7.75_{-0.01}^{+0.01}$ ($Z/Z_\odot = 0.12$) compared to local counterparts. We discuss possible scenarios for elevated N/O abundance in ID60001, including pristine gas inflow, Wolf-Rayet (WR) stars, and Oxygen depletion by Type II supernova winds. Based on the moderately broadened He{\sc ii}$λ$4686 emission line, galaxy morphology, and star-formation history, we conclude that the elevated N/O abundance of ID60001 is likely originated from massive ($>25\,M_\odot$) WR stars that directly collapse into a black hole. We also stress the importance of reliable electron density measurements when deriving N/O abundance with rest-frame optical emission lines. |
| title | Potential Nitrogen Enrichment via Direct-Collapse Wolf-Rayet Stars in a $z=4.7$ Star-Forming Galaxy |
| topic | Astrophysics of Galaxies |
| url | https://arxiv.org/abs/2502.04817 |