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| Main Authors: | , , , , , , , , , , , , , , |
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| Format: | Preprint |
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2025
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| Subjects: | |
| Online Access: | https://arxiv.org/abs/2503.11457 |
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| _version_ | 1866912573724557312 |
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| author | Nakane, Minami Ouchi, Masami Nakajima, Kimihiko Ono, Yoshiaki Harikane, Yuichi Isobe, Yuki Nomoto, Ken'ichi Ishigaki, Miho N. Yanagisawa, Hiroto Kashino, Daichi Tominaga, Nozomu Takahashi, Koh Nishigaki, Moka Takeda, Yui Watanabe, Kuria |
| author_facet | Nakane, Minami Ouchi, Masami Nakajima, Kimihiko Ono, Yoshiaki Harikane, Yuichi Isobe, Yuki Nomoto, Ken'ichi Ishigaki, Miho N. Yanagisawa, Hiroto Kashino, Daichi Tominaga, Nozomu Takahashi, Koh Nishigaki, Moka Takeda, Yui Watanabe, Kuria |
| contents | We derive Fe-abundance ratios of 7 galaxies at $z=9-12$ with $-22<M_{\mathrm{UV}}<-19$ whose JWST/NIRSpec spectra achieve very high signal-to-noise ratios, $\mathrm{SNR}=60-320$, at the rest-frame UV wavelength. We fit stellar population synthesis model spectra to these JWST spectra, masking out nebular emission lines, and obtain Fe-abundance ratios of $\mathrm{[Fe/H]}=-1-0$ dex for 5 galaxies and upper limits of $\mathrm{[Fe/H]}\sim-2-0$ dex for 2 galaxies. We compare these [Fe/H] values with the oxygen abundances of these galaxies ($7.4<12+\log{\mathrm{(O/H)}}<8.4$) in the same manner as previous studies of $z\sim2-6$ galaxies, and derive oxygen-to-iron abundance ratios [O/Fe]. We find that 2 out of 7 galaxies, GS-z11-0 and GN-z11, show Fe enhancements relative to O ($\mathrm{[O/Fe]}<0$ dex), especially GS-z11-0 ($z=11.12$) with a Fe enhancement ($\mathrm{[O/Fe]}=-0.68_{-0.55}^{+0.37}$ dex) beyond the solar-abundance ratio at $\sim2σ$. Because, unlike GS-z11-0, GN-z11 ($z=10.60$) may be an AGN, we constrain [O/Fe] via FeII emission under the assumption of AGN and confirm that the Fe enhancement is consistent even in the case of AGN. While [O/Fe] values of most galaxies are comparable to those of core-collapse supernovae (CCSNe) yields, the Fe enhancements of GS-z11-0 and GN-z11 are puzzling. We develop chemical evolution models, and find that the Fe enhancements in GS-z11-0 and GN-z11 can be explained by 1) pair-instability supernovae/bright hypernovae with little contribution of CCSNe or 2) Type-Ia supernovae with short delay time ($\sim30-50$ Myr) with a top-light initial mass function. |
| format | Preprint |
| id |
arxiv_https___arxiv_org_abs_2503_11457 |
| institution | arXiv |
| publishDate | 2025 |
| record_format | arxiv |
| spellingShingle | Fe Abundances of Early Galaxies at $z=9-12$ Derived with Deep JWST Spectra Nakane, Minami Ouchi, Masami Nakajima, Kimihiko Ono, Yoshiaki Harikane, Yuichi Isobe, Yuki Nomoto, Ken'ichi Ishigaki, Miho N. Yanagisawa, Hiroto Kashino, Daichi Tominaga, Nozomu Takahashi, Koh Nishigaki, Moka Takeda, Yui Watanabe, Kuria Astrophysics of Galaxies We derive Fe-abundance ratios of 7 galaxies at $z=9-12$ with $-22<M_{\mathrm{UV}}<-19$ whose JWST/NIRSpec spectra achieve very high signal-to-noise ratios, $\mathrm{SNR}=60-320$, at the rest-frame UV wavelength. We fit stellar population synthesis model spectra to these JWST spectra, masking out nebular emission lines, and obtain Fe-abundance ratios of $\mathrm{[Fe/H]}=-1-0$ dex for 5 galaxies and upper limits of $\mathrm{[Fe/H]}\sim-2-0$ dex for 2 galaxies. We compare these [Fe/H] values with the oxygen abundances of these galaxies ($7.4<12+\log{\mathrm{(O/H)}}<8.4$) in the same manner as previous studies of $z\sim2-6$ galaxies, and derive oxygen-to-iron abundance ratios [O/Fe]. We find that 2 out of 7 galaxies, GS-z11-0 and GN-z11, show Fe enhancements relative to O ($\mathrm{[O/Fe]}<0$ dex), especially GS-z11-0 ($z=11.12$) with a Fe enhancement ($\mathrm{[O/Fe]}=-0.68_{-0.55}^{+0.37}$ dex) beyond the solar-abundance ratio at $\sim2σ$. Because, unlike GS-z11-0, GN-z11 ($z=10.60$) may be an AGN, we constrain [O/Fe] via FeII emission under the assumption of AGN and confirm that the Fe enhancement is consistent even in the case of AGN. While [O/Fe] values of most galaxies are comparable to those of core-collapse supernovae (CCSNe) yields, the Fe enhancements of GS-z11-0 and GN-z11 are puzzling. We develop chemical evolution models, and find that the Fe enhancements in GS-z11-0 and GN-z11 can be explained by 1) pair-instability supernovae/bright hypernovae with little contribution of CCSNe or 2) Type-Ia supernovae with short delay time ($\sim30-50$ Myr) with a top-light initial mass function. |
| title | Fe Abundances of Early Galaxies at $z=9-12$ Derived with Deep JWST Spectra |
| topic | Astrophysics of Galaxies |
| url | https://arxiv.org/abs/2503.11457 |