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Peer-reviewedCC BYThe Astrophysical Journal

A Fleeting GLIMPSE of N/O Enrichment at Cosmic Dawn: Evidence for Wolf Rayet N Stars in a z = 6.1 Galaxy

  • Danielle A. Berg1
  • Rohan P. Naidu2
  • John Chisholm1
  • Hakim Atek3
  • Seiji Fujimoto4
  • Vasily Kokorev1
  • Lukas J. Furtak1
  • Chiaki Kobayashi5
  • D. Schaerer6,7
  • Angela Adamo8
  • Qinyue Fei4
  • Damien Korber7
10 more authors
  • Jorryt Matthee9
  • R. Marques-Chaves7
  • Zorayda Martinez1
  • Kristen B. W. McQuinn10,11
  • Julián B. Muñoz1
  • Pascal A. Oesch7,12
  • Alberto Saldana-Lopez8
  • Daniel P. Stark13
  • Mabel G. Stephenson1
  • Tiger Yu-Yang Hsiao1
13 affiliations
  1. 1The University of Texas at Austin
  2. 2MIT Kavli Institute for Astrophysics and Space Research
  3. 3Sorbonne Université
  4. 4University of Toronto
  5. 5University of Hertfordshire
  6. 6CNRS
  7. 7Universite de Geneve
  8. 8Stockholm University
  9. 9Institute of Science and Technology Austria (ISTA)
  10. 10Rutgers University
  11. 11Space Telescope Science Institute
  12. 12University of Copenhagen
  13. 13University of California
Open at sourceDOICite

Abstract

We present the discovery of extreme nitrogen enrichment by Wolf Rayet nitrogen (WN) stars in the metal-poor (∼10% Z ⊙ ), lensed, compact ( R eff ∼ 20 pc) galaxy RXCJ2248 at z = 6.1, revealed by unprecedentedly deep JWST/NIRSpec medium-resolution spectroscopy from the GLIMPSE-D Survey. The exquisite signal-to-noise ratio reveals multiple high-ionization nebular lines and broad Balmer and [O iii ] components (FWHM ∼700–3000 km s −1 ). We detect broadened He ii λ 1640 and λ 4687 (FWHM ∼ 530 km s −1 ) and strong N iii λ 4642 emission consistent with a population of WN stars, making RXCJ2248 the most distant galaxy with confirmed Wolf Rayet (WR) features to date. We measure the multiphase nebular density across five ions, the direct-method metallicity ( 12 + log ( O / H ) = 7.753 ± 0.025 ), and a nonuniform elemental enrichment pattern of extreme N/O enhancement ( log ( N / O ) = − 0.391 ± 0.037 from N + , N +2 , and N +3 ) but suppressed C/O relative to empirical C/N trends. We show that this abundance pattern can be explained by enrichment from a dual-burst with a low WR carbon/WN ratio, as expected at low metallicities. Crucially, these signatures can only arise during a brief, rare evolutionary window shortly after a burst (∼3–6 Myr), when WN stars dominate chemical feedback but before dilution by later yields (e.g., supernovae). The observed frequency of strong N emitters at high− z implies a ∼50 Myr burst duty cycle, suggesting that N/O outliers may represent a brief but ubiquitous phase in the evolution of highly star-forming early galaxies. The WN detection in RXCJ2248, therefore, provides the first direct evidence of WR-driven nitrogen enrichment in the first billion years of the Universe and a novel timing argument for the bursty star formation cycles that shaped galaxies at cosmic dawn.

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Cite

BibTeXRIS
BibTeX
@article{berg2026fleeting,
  title = {{A Fleeting GLIMPSE of N/O Enrichment at Cosmic Dawn: Evidence for Wolf Rayet N Stars in a z = 6.1 Galaxy}},
  author = {Danielle A. Berg and Rohan P. Naidu and John Chisholm and Hakim Atek and Seiji Fujimoto and Vasily Kokorev and Lukas J. Furtak and Chiaki Kobayashi and D. Schaerer and Angela Adamo and Qinyue Fei and Damien Korber and Jorryt Matthee and R. Marques-Chaves and Zorayda Martinez and Kristen B. W. McQuinn and Julián B. Muñoz and Pascal A. Oesch and Alberto Saldana-Lopez and Daniel P. Stark and Mabel G. Stephenson and Tiger Yu-Yang Hsiao},
  journal = {The Astrophysical Journal},
  year = {2026},
  month = may,
  doi = {10.3847/1538-4357/ae5e4c},
  url = {https://doi.org/10.3847/1538-4357/ae5e4c},
  note = {CC BY},
}
RIS
TY  - JOUR
TI  - A Fleeting GLIMPSE of N/O Enrichment at Cosmic Dawn: Evidence for Wolf Rayet N Stars in a z = 6.1 Galaxy
AU  - Danielle A. Berg
AU  - Rohan P. Naidu
AU  - John Chisholm
AU  - Hakim Atek
AU  - Seiji Fujimoto
AU  - Vasily Kokorev
AU  - Lukas J. Furtak
AU  - Chiaki Kobayashi
AU  - D. Schaerer
AU  - Angela Adamo
AU  - Qinyue Fei
AU  - Damien Korber
AU  - Jorryt Matthee
AU  - R. Marques-Chaves
AU  - Zorayda Martinez
AU  - Kristen B. W. McQuinn
AU  - Julián B. Muñoz
AU  - Pascal A. Oesch
AU  - Alberto Saldana-Lopez
AU  - Daniel P. Stark
AU  - Mabel G. Stephenson
AU  - Tiger Yu-Yang Hsiao
PY  - 2026
DA  - 2026/05/20
JO  - The Astrophysical Journal
DO  - 10.3847/1538-4357/ae5e4c
UR  - https://doi.org/10.3847/1538-4357/ae5e4c
AB  - We present the discovery of extreme nitrogen enrichment by Wolf Rayet nitrogen (WN) stars in the metal-poor (∼10% Z ⊙ ), lensed, compact ( R eff ∼ 20 pc) galaxy RXCJ2248 at z = 6.1, revealed by unprecedentedly deep JWST/NIRSpec medium-resolution spectroscopy from the GLIMPSE-D Survey. The exquisite signal-to-noise ratio reveals multiple high-ionization nebular lines and broad Balmer and [O iii ] components (FWHM ∼700–3000 km s −1 ). We detect broadened He ii λ 1640 and λ 4687 (FWHM ∼ 530 km s −1 ) and strong N iii λ 4642 emission consistent with a population of WN stars, making RXCJ2248 the most distant galaxy with confirmed Wolf Rayet (WR) features to date. We measure the multiphase nebular density across five ions, the direct-method metallicity ( 12 + log ( O / H ) = 7.753 ± 0.025 ), and a nonuniform elemental enrichment pattern of extreme N/O enhancement ( log ( N / O ) = − 0.391 ± 0.037 from N + , N +2 , and N +3 ) but suppressed C/O relative to empirical C/N trends. We show that this abundance pattern can be explained by enrichment from a dual-burst with a low WR carbon/WN ratio, as expected at low metallicities. Crucially, these signatures can only arise during a brief, rare evolutionary window shortly after a burst (∼3–6 Myr), when WN stars dominate chemical feedback but before dilution by later yields (e.g., supernovae). The observed frequency of strong N emitters at high− z implies a ∼50 Myr burst duty cycle, suggesting that N/O outliers may represent a brief but ubiquitous phase in the evolution of highly star-forming early galaxies. The WN detection in RXCJ2248, therefore, provides the first direct evidence of WR-driven nitrogen enrichment in the first billion years of the Universe and a novel timing argument for the bursty star formation cycles that shaped galaxies at cosmic dawn.
SN  - 0004-637X
SN  - 1538-4357
ER  -