EMPRESS. X. Spatially resolved mass-metallicity relation in extremely metal-poor galaxies: evidence of episodic star-formation fueled by a metal-poor gas infall
| Autor: | Nakajima, Kimihiko, Ouchi, Masami, Isobe, Yuki, Xu, Yi, Ozaki, Shinobu, Nagao, Tohru, Inoue, Akio K., Rauch, Michael, Kusakabe, Haruka, Onodera, Masato, Nishigaki, Moka, Ono, Yoshiaki, Sugahara, Yuma, Hattori, Takashi, Hirai, Yutaka, Hashimoto, Takuya, Kim, Ji Hoon, Moriya, Takashi J., Yanagisawa, Hiroto, Aoyama, Shohei, Fujimoto, Seiji, Fukushima, Hajime, Fukushima, Keita, Harikane, Yuichi, Hatano, Shun, Hayashi, Kohei, Ishigaki, Tsuyoshi, Kawasaki, Masahiro, Kojima, Takashi, Komiyama, Yutaka, Koyama, Shuhei, Koyama, Yusei, Lee, Chien-Hsiu, Matsumoto, Akinori, Mawatari, Ken, Motohara, Kentaro, Murai, Kai, Nagamine, Kentaro, Nakane, Minami, Saito, Tomoki, Sasaki, Rin, Shibuya, Takatoshi, Suzuki, Akihiro, Takeuchi, Tsutomu T., Umeda, Hiroya, Umemura, Masayuki, Watanabe, Kuria, Yabe, Kiyoto, Yajima, Hidenobu, Zhang, Yechi |
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| Rok vydání: | 2024 |
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| Druh dokumentu: | Working Paper |
| Popis: | Using the Subaru/FOCAS IFU capability, we examine the spatially resolved relationships between gas-phase metallicity, stellar mass, and star-formation rate surface densities (Sigma_* and Sigma_SFR, respectively) in extremely metal-poor galaxies (EMPGs) in the local universe. Our analysis includes 24 EMPGs, comprising 9,177 spaxels, which span a unique parameter space of local metallicity (12+log(O/H) = 6.9 to 7.9) and stellar mass surface density (Sigma_* ~ 10^5 to 10^7 Msun/kpc^2), extending beyond the range of existing large integral-field spectroscopic surveys. Through spatially resolved emission line diagnostics based on the [NII] BPT-diagram, we verify the absence of evolved active galactic nuclei in these EMPGs. Our findings reveal that, while the resolved mass-metallicity relation exhibits significant scatter in the low-mass regime, this scatter is closely correlated with local star-formation surface density. Specifically, metallicity decreases as Sigma_SFR increases for a given Sigma_*. Notably, half of the EMPGs show a distinct metal-poor horizontal branch on the resolved mass-metallicity relation. This feature typically appears at the peak clump with the highest Sigma_* and Sigma_SFR and is surrounded by a relatively metal-enriched ambient region. These findings support a scenario in which metal-poor gas infall fuels episodic star formation in EMPGs, consistent with the kinematic properties observed in these systems. In addition, we identify four EMPGs with exceptionally low central metallicities (12+log(O/H) <~ 7.2), which display only a metal-poor clump without a surrounding metal-rich region. This suggests that such ultra-low metallicity EMPGs, at less than a few percent of the solar metallicity, may serve as valuable analogs for galaxies in the early stages of galaxy evolution. Comment: 29 pages, 14 figures. Submitted to ApJ |
| Databáze: | arXiv |
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