February
2026
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2026ApJ...998..141Z
Authors
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Zhang, Yechi
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Morishita, Takahiro
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Stiavelli, Massimo
Abstract
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We present analyses of a nitrogen-enriched star-forming galaxy, ID60001, at z = 4.6928 based on James Webb Space Telescope/NIRSpec Multi-Object 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(N/O)=−0.76−0.03+0.03 ( [N/O]=0.10−0.03+0.03 ), which is significantly elevated at the corresponding metallicity 12+log(O/H)=7.75−0.01+0.01 (Z/Z⊙ = 0.12) compared to local counterparts. We discuss possible scenarios for elevated N/O abundance in ID60001, including pristine gas inflow, Wolf─Rayet (W-R) stars, and oxygen depletion by Type II supernova winds. Based on the moderately broadened He IIλ4686 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⊙) W-R 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.
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