EMPRESS. II. Highly Fe-enriched Metal-poor Galaxies with similar to 1.0 (Fe/O)(circle dot) and 0.02 (O/H)(circle dot): Possible Traces of Supermassive (>300 M (circle dot)) Stars in Early Galaxies* dagger double dagger
Publikation: Bidrag til tidsskrift › Tidsskriftartikel › Forskning › fagfællebedømt
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EMPRESS. II. Highly Fe-enriched Metal-poor Galaxies with similar to 1.0 (Fe/O)(circle dot) and 0.02 (O/H)(circle dot) : Possible Traces of Supermassive (>300 M (circle dot)) Stars in Early Galaxies* dagger double dagger. / Kojima, Takashi; Ouchi, Masami; Rauch, Michael; Ono, Yoshiaki; Nakajima, Kimihiko; Isobe, Yuki; Fujimoto, Seiji; Harikane, Yuichi; Hashimoto, Takuya; Hayashi, Masao; Komiyama, Yutaka; Kusakabe, Haruka; Kim, Ji Hoon; Lee, Chien-Hsiu; Mukae, Shiro; Nagao, Tohru; Onodera, Masato; Shibuya, Takatoshi; Sugahara, Yuma; Umemura, Masayuki; Yabe, Kiyoto.
I: Astrophysical Journal, Bind 913, Nr. 1, 22, 19.05.2021.Publikation: Bidrag til tidsskrift › Tidsskriftartikel › Forskning › fagfællebedømt
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TY - JOUR
T1 - EMPRESS. II. Highly Fe-enriched Metal-poor Galaxies with similar to 1.0 (Fe/O)(circle dot) and 0.02 (O/H)(circle dot)
T2 - Possible Traces of Supermassive (>300 M (circle dot)) Stars in Early Galaxies* dagger double dagger
AU - Kojima, Takashi
AU - Ouchi, Masami
AU - Rauch, Michael
AU - Ono, Yoshiaki
AU - Nakajima, Kimihiko
AU - Isobe, Yuki
AU - Fujimoto, Seiji
AU - Harikane, Yuichi
AU - Hashimoto, Takuya
AU - Hayashi, Masao
AU - Komiyama, Yutaka
AU - Kusakabe, Haruka
AU - Kim, Ji Hoon
AU - Lee, Chien-Hsiu
AU - Mukae, Shiro
AU - Nagao, Tohru
AU - Onodera, Masato
AU - Shibuya, Takatoshi
AU - Sugahara, Yuma
AU - Umemura, Masayuki
AU - Yabe, Kiyoto
PY - 2021/5/19
Y1 - 2021/5/19
N2 - We present element abundance ratios and ionizing radiation of local young low-mass (similar to 10(6) M (circle dot)) extremely metal-poor galaxies (EMPGs) with a 2% solar oxygen abundance (O/H)(circle dot) and a high specific star formation rate (sSFR similar to 300 Gyr(-1)) and other (extremely) metal-poor galaxies, which are compiled from Extremely Metal-Poor Representatives Explored by the Subaru Survey (EMPRESS) and the literature. Weak emission lines such as [Fe iii] lambda 4658 and He ii lambda 4686 are detected in very deep optical spectra of the EMPGs taken with 8 m class telescopes, including Keck and Subaru, enabling us to derive element abundance ratios with photoionization models. We find that neon-to-oxygen and argon-to-oxygen ratios are comparable to those of known local dwarf galaxies and that the nitrogen-to-oxygen abundance ratios (N/O) are lower than 20% (N/O)(circle dot), consistent with the low oxygen abundance. However, the iron-to-oxygen abundance ratios (Fe/O) of the EMPGs are generally high; the EMPGs with the 2%-solar oxygen abundance show high Fe/O ratios of similar to 90%-140% (Fe/O)(circle dot), which are unlikely to be explained by suggested scenarios of Type Ia supernova iron productions, iron's dust depletion, and metal-poor gas inflow onto previously metal-riched galaxies with solar abundances. Moreover, the EMPGs with the 2%-solar oxygen abundance have very high He ii lambda 4686/H beta ratios of similar to 1/40, which are not reproduced by existing models of high-mass X-ray binaries with progenitor stellar masses M (circle dot). Comparing stellar-nucleosynthesis and photoionization models with a comprehensive sample of EMPGs identified by this and previous EMPG studies, we propose that both the high Fe/O ratios and the high He ii lambda 4686/H beta ratios are explained by the past existence of supermassive (>300 M (circle dot)) stars, which may evolve into intermediate-mass black holes (greater than or similar to 100 M (circle dot)).
AB - We present element abundance ratios and ionizing radiation of local young low-mass (similar to 10(6) M (circle dot)) extremely metal-poor galaxies (EMPGs) with a 2% solar oxygen abundance (O/H)(circle dot) and a high specific star formation rate (sSFR similar to 300 Gyr(-1)) and other (extremely) metal-poor galaxies, which are compiled from Extremely Metal-Poor Representatives Explored by the Subaru Survey (EMPRESS) and the literature. Weak emission lines such as [Fe iii] lambda 4658 and He ii lambda 4686 are detected in very deep optical spectra of the EMPGs taken with 8 m class telescopes, including Keck and Subaru, enabling us to derive element abundance ratios with photoionization models. We find that neon-to-oxygen and argon-to-oxygen ratios are comparable to those of known local dwarf galaxies and that the nitrogen-to-oxygen abundance ratios (N/O) are lower than 20% (N/O)(circle dot), consistent with the low oxygen abundance. However, the iron-to-oxygen abundance ratios (Fe/O) of the EMPGs are generally high; the EMPGs with the 2%-solar oxygen abundance show high Fe/O ratios of similar to 90%-140% (Fe/O)(circle dot), which are unlikely to be explained by suggested scenarios of Type Ia supernova iron productions, iron's dust depletion, and metal-poor gas inflow onto previously metal-riched galaxies with solar abundances. Moreover, the EMPGs with the 2%-solar oxygen abundance have very high He ii lambda 4686/H beta ratios of similar to 1/40, which are not reproduced by existing models of high-mass X-ray binaries with progenitor stellar masses M (circle dot). Comparing stellar-nucleosynthesis and photoionization models with a comprehensive sample of EMPGs identified by this and previous EMPG studies, we propose that both the high Fe/O ratios and the high He ii lambda 4686/H beta ratios are explained by the past existence of supermassive (>300 M (circle dot)) stars, which may evolve into intermediate-mass black holes (greater than or similar to 100 M (circle dot)).
KW - ELECTRON-IMPACT EXCITATION
KW - EMISSION-LINE GALAXIES
KW - DIGITAL SKY SURVEY
KW - X-RAY BINARIES
KW - PRESSURE-DOMINATED PHOTOIONIZATION
KW - HARD IONIZING SPECTRUM
KW - LY-ALPHA EMITTERS
KW - FORMING GALAXIES
KW - TRANSITION-PROBABILITIES
KW - COLLISION STRENGTHS
U2 - 10.3847/1538-4357/abec3d
DO - 10.3847/1538-4357/abec3d
M3 - Journal article
VL - 913
JO - Astrophysical Journal
JF - Astrophysical Journal
SN - 0004-637X
IS - 1
M1 - 22
ER -
ID: 270619413