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arXiv · 2407.14470

Low [O/Fe] Ratio in a Luminous Galaxy at the Early Cosmic Epoch ($z>10$): Signature of Short Delay Time or Bright Hypernovae/Pair-Instability Supernovae?

Minami Nakane·Masami Ouchi·Kimihiko Nakajima·Yuichi Harikane·Nozomu Tominaga·Koh Takahashi·Daichi Kashino·Hiroto Yanagisawa·Kuria Watanabe·Ken'ichi Nomoto·Yuki Isobe·Moka Nishigaki·Miho N. Ishigaki·Yoshiaki Ono·Yui Takeda
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Abstract

We present an [O/Fe] ratio of a luminous galaxy GN-z11 at $z=10.60$ derived with the deep public JWST/NIRSpec data. We fit the medium-resolution grating (G140M, G235M, and G395M) data with the model spectra consisting of BPASS-stellar and CLOUDY-nebular spectra in the rest-frame UV wavelength ranges with Fe absorption lines, carefully masking out the other emission and absorption lines in the same manner as previous studies conducted for lower redshift ($z\sim 2-6$) galaxies with oxygen abundance measurements. We obtain an Fe-rich abundance ratio $\mathrm{[O/Fe]}=-0.37^{+0.43}_{-0.22}$, which is confirmed with the independent deep prism data as well as by the classic 1978 index method. This [O/Fe] measurement is lower than measured for star-forming galaxies at $z\sim 2-3$. Because $z=10.60$ is an early epoch after the Big Bang ($\sim 430$ Myr) and the first star formation (likely $\sim 200$ Myr), it is difficult to produce Fe by Type Ia supernovae (SNeIa) requiring sufficient delay time for white-dwarf formation and gas accretion. The Fe-rich abundance ratio in GN-z11 suggests that the delay time is short, or that the major Fe enrichment is not accomplished by SNeIa but bright hypernovae (BrHNe) and/or pair-instability supernovae (PISNe), where the yield models of BrHNe and PISNe explain Fe, Ne, and O abundance ratios of GN-z11. The [O/Fe] measurement is not too low to rule out the connection between GN-z11 and globular clusters (GCs) previously suggested by the nitrogen abundance, but rather supports the connection with a GC population at high [N/O] if a metal dilution process exists.

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Minami Nakane, Masami Ouchi, Kimihiko Nakajima, Yuichi Harikane, Nozomu Tominaga, Koh Takahashi, Daichi Kashino, Hiroto Yanagisawa, Kuria Watanabe, Ken'ichi Nomoto, Yuki Isobe, Moka Nishigaki, Miho N. Ishigaki, Yoshiaki Ono, Yui Takeda. 2024-07-19. Low [O/Fe] Ratio in a Luminous Galaxy at the Early Cosmic Epoch ($z>10$): Signature of Short Delay Time or Bright Hypernovae/Pair-Instability Supernovae?. https://arxiv.org/abs/2407.14470

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