Discovery of new N-emitters over a wide redshift range
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| Format: | Preprint |
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2025
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| _version_ | 1866908675663200256 |
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| author | Morel, I. Schaerer, D. Marques-Chaves, R. Prantzos, N. Charbonnel, C. Brammer, G. Xiao, M. Dessauges-Zavadsky, M. |
| author_facet | Morel, I. Schaerer, D. Marques-Chaves, R. Prantzos, N. Charbonnel, C. Brammer, G. Xiao, M. Dessauges-Zavadsky, M. |
| contents | JWST observations have revealed rare galaxies with UV spectra exhibiting intense lines of nitrogen, indicative of super-solar N/O abundances at low metallicity. To better understand these enigmatic objects and provide new constraints on proposed scenarios, we have undertaken a systematic search for galaxies with UV emission lines of nitrogen. Using public JWST NIRSpec data, we have identified 45 N-emitters with robust NIII] or NIV] detections, including 4 previously known objects. We find N-emitters from redshift $z\sim 3-11$ among a broad diversity of galaxies, in terms of morphology, UV magnitude, stellar mass, SFR, metallicity, and rest-optical line strengths. The UV nitrogen lines show typical equivalent widths between $\sim 5-50$ Å. Carbon lines are generally fainter than the N lines. Using strong line calibrations established at high-redshift, we find metallicities $12+log(O/H)\sim 7.15-8.5$, including thus also high metallicities. The H$β$ equivalent width of N-emitters varies strongly, and sources with low EWs show clear signs of a Balmer break, indicative of composite stellar populations combining both young (< 10 Myr) stars responsible of the UV emission lines and an older population contributing to the rest-optical spectrum. Supersolar N/O ratios are found in all N-emitters. C/O abundances are comparable to those of galaxies at the same metallicity, and all N-emitters show high N/C ratios or lower limits ($\log(N/C) > 0.5$), independently of metallicity. The observed abundance ratios are compatible with ejecta from H-burning and do not show signs of Carbon enhancements, even at higher metallicities. Finally, we find that the fraction of N-emitters increases with redshift, and we quantify this evolution. Our study increases the sample of known N-emitters by a factor $\sim 3$, reveals a diversity of properties among N-emitters, and provides new constraints on their nature. |
| format | Preprint |
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arxiv_https___arxiv_org_abs_2511_20484 |
| institution | arXiv |
| publishDate | 2025 |
| record_format | arxiv |
| spellingShingle | Discovery of new N-emitters over a wide redshift range Morel, I. Schaerer, D. Marques-Chaves, R. Prantzos, N. Charbonnel, C. Brammer, G. Xiao, M. Dessauges-Zavadsky, M. Astrophysics of Galaxies JWST observations have revealed rare galaxies with UV spectra exhibiting intense lines of nitrogen, indicative of super-solar N/O abundances at low metallicity. To better understand these enigmatic objects and provide new constraints on proposed scenarios, we have undertaken a systematic search for galaxies with UV emission lines of nitrogen. Using public JWST NIRSpec data, we have identified 45 N-emitters with robust NIII] or NIV] detections, including 4 previously known objects. We find N-emitters from redshift $z\sim 3-11$ among a broad diversity of galaxies, in terms of morphology, UV magnitude, stellar mass, SFR, metallicity, and rest-optical line strengths. The UV nitrogen lines show typical equivalent widths between $\sim 5-50$ Å. Carbon lines are generally fainter than the N lines. Using strong line calibrations established at high-redshift, we find metallicities $12+log(O/H)\sim 7.15-8.5$, including thus also high metallicities. The H$β$ equivalent width of N-emitters varies strongly, and sources with low EWs show clear signs of a Balmer break, indicative of composite stellar populations combining both young (< 10 Myr) stars responsible of the UV emission lines and an older population contributing to the rest-optical spectrum. Supersolar N/O ratios are found in all N-emitters. C/O abundances are comparable to those of galaxies at the same metallicity, and all N-emitters show high N/C ratios or lower limits ($\log(N/C) > 0.5$), independently of metallicity. The observed abundance ratios are compatible with ejecta from H-burning and do not show signs of Carbon enhancements, even at higher metallicities. Finally, we find that the fraction of N-emitters increases with redshift, and we quantify this evolution. Our study increases the sample of known N-emitters by a factor $\sim 3$, reveals a diversity of properties among N-emitters, and provides new constraints on their nature. |
| title | Discovery of new N-emitters over a wide redshift range |
| topic | Astrophysics of Galaxies |
| url | https://arxiv.org/abs/2511.20484 |