Deep Rest-UV JWST/NIRSpec Spectroscopy of Early Galaxies: The Demographics of C iv and N-emitters in the Reionization Era
JWST has recently discovered a subset of reionization era galaxies with ionized gas that is metal-poor in oxygen and carbon but heavily enriched in nitrogen. This abundance pattern is almost never seen in lower-redshift galaxies but is commonly observed in globular cluster stars. We have recently de...
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2025-01-01
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| Online Access: | https://doi.org/10.3847/1538-4357/ada95c |
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| author | Michael W. Topping Daniel P. Stark Peter Senchyna Zuyi Chen Adi Zitrin Ryan Endsley Stéphane Charlot Lukas J. Furtak Michael V. Maseda Adele Plat Renske Smit Ramesh Mainali Jacopo Chevallard Stephen Molyneux Jane R. Rigby |
| author_facet | Michael W. Topping Daniel P. Stark Peter Senchyna Zuyi Chen Adi Zitrin Ryan Endsley Stéphane Charlot Lukas J. Furtak Michael V. Maseda Adele Plat Renske Smit Ramesh Mainali Jacopo Chevallard Stephen Molyneux Jane R. Rigby |
| author_sort | Michael W. Topping |
| collection | DOAJ |
| description | JWST has recently discovered a subset of reionization era galaxies with ionized gas that is metal-poor in oxygen and carbon but heavily enriched in nitrogen. This abundance pattern is almost never seen in lower-redshift galaxies but is commonly observed in globular cluster stars. We have recently demonstrated that this peculiar abundance pattern appears in a compact (≃20 pc) metal-poor galaxy undergoing a strong burst of star formation. This galaxy was originally selected based on strong C iv emission, indicating a hard radiation field rarely seen locally. In this paper, we present JWST/NIRSpec observations of another reionization-era galaxy known to power strong C iv emission, the z = 7.04 gravitationally lensed galaxy A1703-zd6. The emission-line spectrum reveals this is a metal-poor galaxy ( $12+\mathrm{log}({\rm{O}}/{\rm{H}})=7.47\pm 0.19$ ) dominated by a young stellar population ( $1.{6}_{-0.4}^{+0.5}$ Myr) that powers a very hard ionizing spectrum (C iv equivalent width, EW = 19.4 Å, He ii EW = 2.2 Å). The interstellar medium is highly enriched in nitrogen ( $\mathrm{log}({\rm{N}}/{\rm{O}})=-0.6$ ) with very high electron densities (8–19 × 10 ^4 cm ^−3 ) and extreme ionization conditions rarely seen at lower redshift. We also find intense CIV emission (EW ≳ 20 Å) in two new z ≳ 6 metal-poor galaxies. To put these results in context, we search for UV line emission in a sample of 737 z ≳ 4 galaxies with NIRSpec spectra, establishing that 40%(30%) of systems with [O iii ]+H β EW > 2000 Å have N iv ] (C iv ) detections with EW > 5 Å(> 10 Å). These results suggest high N/O ratios, and hard ionizing sources appear in a brief phase following a burst of star formation in compact high-density stellar complexes. |
| format | Article |
| id | doaj-art-8d9c313211ba40328c19572952296982 |
| institution | DOAJ |
| issn | 1538-4357 |
| language | English |
| publishDate | 2025-01-01 |
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| spelling | doaj-art-8d9c313211ba40328c195729522969822025-08-20T03:05:03ZengIOP PublishingThe Astrophysical Journal1538-43572025-01-01980222510.3847/1538-4357/ada95cDeep Rest-UV JWST/NIRSpec Spectroscopy of Early Galaxies: The Demographics of C iv and N-emitters in the Reionization EraMichael W. Topping0Daniel P. Stark1Peter Senchyna2https://orcid.org/0000-0002-9132-6561Zuyi Chen3https://orcid.org/0000-0002-2178-5471Adi Zitrin4https://orcid.org/0000-0002-0350-4488Ryan Endsley5https://orcid.org/0000-0003-4564-2771Stéphane Charlot6https://orcid.org/0000-0003-3458-2275Lukas J. Furtak7https://orcid.org/0000-0001-6278-032XMichael V. Maseda8https://orcid.org/0000-0003-0695-4414Adele Plat9Renske Smit10https://orcid.org/0000-0001-8034-7802Ramesh Mainali11https://orcid.org/0000-0003-0094-6827Jacopo Chevallard12https://orcid.org/0000-0002-7636-0534Stephen Molyneux13Jane R. Rigby14https://orcid.org/0000-0002-7627-6551Department of Astronomy / Steward Observatory, University of Arizona , 933 N Cherry Avenue, Tucson, AZ 85721, USA ; michaeltopping@arizona.eduDepartment of Astronomy, University of California , Berkeley, CA 94720, USAThe Observatories of the Carnegie Institution for Science , 813 Santa Barbara Street, Pasadena, CA 91101, USADepartment of Astronomy / Steward Observatory, University of Arizona , 933 N Cherry Avenue, Tucson, AZ 85721, USA ; michaeltopping@arizona.eduPhysics Department, Ben-Gurion University of the Negev , P.O. Box 653, Be’er-Sheva 84105, IsraelDepartment of Astronomy, University of Texas , Austin, TX 78712, USASorbonne Université, CNRS , UMR 7095, Institut d’Astrophysique de Paris, 98 bis bd Arago, 75014 Paris, FrancePhysics Department, Ben-Gurion University of the Negev , P.O. Box 653, Be’er-Sheva 84105, IsraelDepartment of Astronomy, University of Wisconsin-Madison , 475 N. Charter Sreet., Madison, WI 53706, USADepartment of Astronomy / Steward Observatory, University of Arizona , 933 N Cherry Avenue, Tucson, AZ 85721, USA ; michaeltopping@arizona.eduAstrophysics Research Institute, Liverpool John Moores University , 146 Brownlow Hill, Liverpool L3 5RF, UKObservational Cosmology Lab, Code 665, NASA Goddard Space Flight Center , 8800 Greenbelt Road, Greenbelt, MD 20771, USADepartment of Physics, University of Oxford , Denys Wilkinson Building, Keble Road, Oxford OX1 3RH, UKAstrophysics Research Institute, Liverpool John Moores University , 146 Brownlow Hill, Liverpool L3 5RF, UK; European Southern Observatory , Karl-Schwarzschild-str. 2, 85748 Garching, GermanyAstrophysics Science Division , Code 660, NASA Goddard Space Flight Center, 8800 Greenbelt Road, Greenbelt, MD 20771, USAJWST has recently discovered a subset of reionization era galaxies with ionized gas that is metal-poor in oxygen and carbon but heavily enriched in nitrogen. This abundance pattern is almost never seen in lower-redshift galaxies but is commonly observed in globular cluster stars. We have recently demonstrated that this peculiar abundance pattern appears in a compact (≃20 pc) metal-poor galaxy undergoing a strong burst of star formation. This galaxy was originally selected based on strong C iv emission, indicating a hard radiation field rarely seen locally. In this paper, we present JWST/NIRSpec observations of another reionization-era galaxy known to power strong C iv emission, the z = 7.04 gravitationally lensed galaxy A1703-zd6. The emission-line spectrum reveals this is a metal-poor galaxy ( $12+\mathrm{log}({\rm{O}}/{\rm{H}})=7.47\pm 0.19$ ) dominated by a young stellar population ( $1.{6}_{-0.4}^{+0.5}$ Myr) that powers a very hard ionizing spectrum (C iv equivalent width, EW = 19.4 Å, He ii EW = 2.2 Å). The interstellar medium is highly enriched in nitrogen ( $\mathrm{log}({\rm{N}}/{\rm{O}})=-0.6$ ) with very high electron densities (8–19 × 10 ^4 cm ^−3 ) and extreme ionization conditions rarely seen at lower redshift. We also find intense CIV emission (EW ≳ 20 Å) in two new z ≳ 6 metal-poor galaxies. To put these results in context, we search for UV line emission in a sample of 737 z ≳ 4 galaxies with NIRSpec spectra, establishing that 40%(30%) of systems with [O iii ]+H β EW > 2000 Å have N iv ] (C iv ) detections with EW > 5 Å(> 10 Å). These results suggest high N/O ratios, and hard ionizing sources appear in a brief phase following a burst of star formation in compact high-density stellar complexes.https://doi.org/10.3847/1538-4357/ada95cGalaxy abundancesGalaxy chemical evolutionHigh-redshift galaxiesGalactic and extragalactic astronomyStarburst galaxies |
| spellingShingle | Michael W. Topping Daniel P. Stark Peter Senchyna Zuyi Chen Adi Zitrin Ryan Endsley Stéphane Charlot Lukas J. Furtak Michael V. Maseda Adele Plat Renske Smit Ramesh Mainali Jacopo Chevallard Stephen Molyneux Jane R. Rigby Deep Rest-UV JWST/NIRSpec Spectroscopy of Early Galaxies: The Demographics of C iv and N-emitters in the Reionization Era The Astrophysical Journal Galaxy abundances Galaxy chemical evolution High-redshift galaxies Galactic and extragalactic astronomy Starburst galaxies |
| title | Deep Rest-UV JWST/NIRSpec Spectroscopy of Early Galaxies: The Demographics of C iv and N-emitters in the Reionization Era |
| title_full | Deep Rest-UV JWST/NIRSpec Spectroscopy of Early Galaxies: The Demographics of C iv and N-emitters in the Reionization Era |
| title_fullStr | Deep Rest-UV JWST/NIRSpec Spectroscopy of Early Galaxies: The Demographics of C iv and N-emitters in the Reionization Era |
| title_full_unstemmed | Deep Rest-UV JWST/NIRSpec Spectroscopy of Early Galaxies: The Demographics of C iv and N-emitters in the Reionization Era |
| title_short | Deep Rest-UV JWST/NIRSpec Spectroscopy of Early Galaxies: The Demographics of C iv and N-emitters in the Reionization Era |
| title_sort | deep rest uv jwst nirspec spectroscopy of early galaxies the demographics of c iv and n emitters in the reionization era |
| topic | Galaxy abundances Galaxy chemical evolution High-redshift galaxies Galactic and extragalactic astronomy Starburst galaxies |
| url | https://doi.org/10.3847/1538-4357/ada95c |
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