| Autor: |
Isobe, Yuki, Ouchi, Masami, Suzuki, Akihiro, Moriya, Takashi J., Nakajima, Kimihiko, Nomoto, Ken’ichi, Rauch, Michael, Harikane, Yuichi, Kojima, Takashi, Ono, Yoshiaki, Fujimoto, Seiji, Inoue, Akio K., Kim, Ji Hoon, Komiyama, Yutaka, Kusakabe, Haruka, Lee, Chien-Hsiu, Maseda, Michael, Matthee, Jorryt, Michel-Dansac, Leo, Nagao, Tohru |
| Předmět: |
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| Zdroj: |
Astrophysical Journal; Feb2022, Vol. 925 Issue 2, p1-18, 18p |
| Abstrakt: |
We present Keck/LRIS follow-up spectroscopy for 13 photometric candidates of extremely metal-poor galaxies (EMPGs) selected by a machine-learning technique applied to the deep (âĽ26 AB mag) optical and wide-area (âĽ500 deg2) Subaru imaging data in the EMPRESS survey. Nine out of the 13 candidates are EMPGs with an oxygen abundance (O/H) less than âĽ10% solar value (O/H)⊙, and four sources are contaminants of moderately metal-rich galaxies or no emission-line objects. Notably, two out of the nine EMPGs have extremely low stellar masses and oxygen abundances of 5 Ă— 104â€"7 Ă— 105 M ⊙ and 2%â€"3% (O/H)⊙, respectively. With a sample of five EMPGs with (Fe/O) measurements, two (three) of which are taken from this study (the literature), we confirm that two EMPGs with the lowest (O/H) ratios of âĽ2% (O/H)⊙ show high (Fe/O) ratios of âĽ0.1, close to the solar abundance ratio. Comparing galaxy chemical enrichment models, we find that the two EMPGs cannot be explained by a scenario of metal-poor gas accretion/episodic star formation history due to their low (N/O) ratios. We conclude that the two EMPGs can be reproduced by the inclusion of bright hypernovae and/or hypothetical pair-instability supernovae (SNe) preferentially produced in a metal-poor environment. This conclusion implies that primordial galaxies at z ⼠10 could have a high abundance of Fe that did not originate from Type Ia SNe with delays and that Fe may not serve as a cosmic clock for primordial galaxies. [ABSTRACT FROM AUTHOR] |
| Databáze: |
Complementary Index |
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