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arXiv · 2407.02575

JADES: The star-formation and chemical enrichment history of a luminous galaxy at z~9.43 probed by ultra-deep JWST/NIRSpec spectroscopy

Mirko Curti·Joris Witstok·Peter Jakobsen·Chiaki Kobayashi·Emma Curtis-Lake·Kevin Hainline·Xihan Ji·Francesco D'Eugenio·Jacopo Chevallard·Roberto Maiolino·Jan Scholtz·Stefano Carniani·Santiago Arribas·William M. Baker·Rachana Bhatawdekar·Kristan Boyett·Andrew J. Bunker·Alex Cameron·Phillip A. Cargile·Stephane Charlot·Daniel J. Eisenstein·Zhiyuan Ji·Benjamin D. Johnson·Nimisha Kumari·Michael V. Maseda·Brant Robertson·Maddie S. Silcock·Sandro Tacchella·Hannah Ubler·Giacomo Venturi·Christina C. Williams·Christopher N. A. Willmer·Chris Willott
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Abstract

We analyse ultra-deep JWST observations of the galaxy JADES-GS-z9-0 at z = 9.4327, and derive detailed stellar and interstellar medium (ISM) properties of this luminous (MUV=-20.43) high-redshift system. Complementary information from NIRCam imaging and NIRSpec (both low- and medium-resolution) spectroscopy reveal a compact system (Re ~110 pc) characterised by a steeply rising star formation history, which is reflected in the inferred young stellar age (t ~ 3 Myr, light-weighted), high star-formation rate surface density ({\Sigma}SFR ~ 72 M yr-1 kpc-2), high ionisation parameter (log(U) ~ -1.5), low metallicity (12+log(O/H) ~ 7.5), and low carbon-over-oxygen abundance ([C/O] = -0.64). Leveraging the detection of N iii]1750 we derive nitrogen-over-oxygen abundance ([N/O] ~ 0) higher than the plateau followed by low-redshift galaxies of similar metallicity, possibly revealing the imprint from (very) massive stars on the ISM enrichment and favouring a top-heavy Initial Mass Function (IMF) scenario. Massive stars powering a hard radiation field are also required to explain the rest-frame UV line ratios, though the presence of the high-excitation [Ne v]{\lambda}3426 emission line possibly hints at additional ionization from an AGN. We also report the tentative detection of Ly{\alpha} emission in the G140M spectrum, shifted by ~450 km/s redward of the systemic redshift. Combined with a modelling of the Ly{\alpha} spectral break, we rule out the presence of very high column densities of neutral gas pertaining to local absorbers, as well as any extended surrounding ionised bubble, suggesting that JADES-GS-z9-0 has not yet significantly contributed to cosmic Reionization.

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Mirko Curti, Joris Witstok, Peter Jakobsen, Chiaki Kobayashi, Emma Curtis-Lake, Kevin Hainline, Xihan Ji, Francesco D'Eugenio, Jacopo Chevallard, Roberto Maiolino, Jan Scholtz, Stefano Carniani, Santiago Arribas, William M. Baker, Rachana Bhatawdekar, Kristan Boyett, Andrew J. Bunker, Alex Cameron, Phillip A. Cargile, Stephane Charlot, Daniel J. Eisenstein, Zhiyuan Ji, Benjamin D. Johnson, Nimisha Kumari, Michael V. Maseda, Brant Robertson, Maddie S. Silcock, Sandro Tacchella, Hannah Ubler, Giacomo Venturi, Christina C. Williams, Christopher N. A. Willmer, Chris Willott. 2024-07-02. JADES: The star-formation and chemical enrichment history of a luminous galaxy at z~9.43 probed by ultra-deep JWST/NIRSpec spectroscopy. https://doi.org/10.1051/0004-6361/202451410

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