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

Danielle A. Berg; Rohan P. Naidu; John Chisholm; Hakim Atek; Seiji Fujimoto; Vasily Kokorev; Lukas J. Furtak; Chiaki Kobayashi; Daniel Schaerer; Angela Adamo; Qinyue Fei; Damien Korber; Jorryt Matthee; Rui Marques-Chaves; Zorayda Martinez; Kristen B. W. Mcquinn; Julian B. Muñoz; Pascal A. Oesch; Daniel P. Stark; Mabel G. Stephenson; Tiger Yu-Yang Hsiao

arXiv · 2511.13591

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

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Abstract

We present the discovery of extreme nitrogen enrichment by Wolf Rayet nitrogen stars (WN) in the metal-poor (~10% Z_odot), 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 S/N reveals multiple high-ionization nebular lines and broad Balmer and [OIII] components (FWHM~700-3000 km/s). We detect broadened HeII 1640 and 4687 (FWHM~530 km/s) and strong NIII] 4642 emission consistent with a population of WN stars, making RXCJ2248 the most distant galaxy with confirmed WR features to date. We measure the multi-phase nebular density across five ions, the direct-method metallicity (12+log(O/H)= 7.749+/-0.023), and a non-uniform elemental enrichment pattern of extreme N/O enhancement (log(N/O)=-0.390+/-0.035 from N^+, N^+2, and N^+3) and 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 WC/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 detection in RXCJ2248, therefore, provides the first direct evidence of WN-driven chemical enrichment in the early Universe and a novel timing argument for the bursty star formation cycles that shaped galaxies at cosmic dawn.

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Danielle A. Berg, Rohan P. Naidu, John Chisholm, Hakim Atek, Seiji Fujimoto, Vasily Kokorev, Lukas J. Furtak, Chiaki Kobayashi, Daniel Schaerer, Angela Adamo, Qinyue Fei, Damien Korber, Jorryt Matthee, Rui Marques-Chaves, Zorayda Martinez, Kristen B. W. Mcquinn, Julian B. Muñoz, Pascal A. Oesch, Daniel P. Stark, Mabel G. Stephenson, Tiger Yu-Yang Hsiao. 2025-11-17. A Fleeting GLIMPSE of N/O Enrichment at Cosmic Dawn: Evidence for Wolf Rayet N Stars in a z = 6.1 Galaxy. https://arxiv.org/abs/2511.13591

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