EMPRESS. IX. Extremely Metal-poor Galaxies are Very Gas-rich Dispersion-dominated Systems: Will the James Webb Space Telescope Witness Gaseous Turbulent High-z Primordial Galaxies?

July 2023 • 2023ApJ...951..102I

Authors • Isobe, Yuki • Ouchi, Masami • Nakajima, Kimihiko • Ozaki, Shinobu • Bouché, Nicolas F. • Wise, John H. • Xu, Yi • Emsellem, Eric • Kusakabe, Haruka • Hattori, Takashi • Nagao, Tohru • Chiaki, Gen • Fukushima, Hajime • Harikane, Yuichi • Hayashi, Kohei • Hirai, Yutaka • Kim, Ji Hoon • Maseda, Michael V. • Nagamine, Kentaro • Shibuya, Takatoshi • Sugahara, Yuma • Yajima, Hidenobu • Aoyama, Shohei • Fujimoto, Seiji • Fukushima, Keita • Hatano, Shun • Inoue, Akio K. • Ishigaki, Tsuyoshi • Kawasaki, Masahiro • Kojima, Takashi • Komiyama, Yutaka • Koyama, Shuhei • Koyama, Yusei • Lee, Chien-Hsiu • Matsumoto, Akinori • Mawatari, Ken • Moriya, Takashi J. • Motohara, Kentaro • Murai, Kai • Nishigaki, Moka • Onodera, Masato • Ono, Yoshiaki • Rauch, Michael • Saito, Tomoki • Sasaki, Rin • Suzuki, Akihiro • Takeuchi, Tsutomu T. • Umeda, Hiroya • Umemura, Masayuki • Watanabe, Kuria • Yabe, Kiyoto • Zhang, Yechi

Abstract • We present kinematics of six local extremely metal-poor galaxies (EMPGs) with low metallicities (0.016-0.098 Z _⊙) and low stellar masses (10^4.7-10^7.6 M _⊙). Taking deep medium/high-resolution (R ~ 7500) integral-field spectra with 8.2 m Subaru, we resolve the small inner velocity gradients and dispersions of the EMPGs with Hα emission. Carefully masking out substructures originating by inflow and/or outflow, we fit three-dimensional disk models to the observed Hα flux, velocity, and velocity dispersion maps. All the EMPGs show rotational velocities (v _rot) of 5-23 km s^-1 smaller than the velocity dispersions (σ ₀) of 17-31 km s^-1, indicating dispersion-dominated (v _rot/σ ₀ = 0.29-0.80 < 1) systems affected by inflow and/or outflow. Except for two EMPGs with large uncertainties, we find that the EMPGs have very large gas-mass fractions of f _gas ≃ 0.9-1.0. Comparing our results with other Hα kinematics studies, we find that v _rot/σ ₀ decreases and f _gas increases with decreasing metallicity, decreasing stellar mass, and increasing specific star formation rate. We also find that simulated high-z (z ~ 7) forming galaxies have gas fractions and dynamics similar to the observed EMPGs. Our EMPG observations and the simulations suggest that primordial galaxies are gas-rich dispersion-dominated systems, which would be identified by the forthcoming James Webb Space Telescope observations at z ~ 7.

Links

• SIMBAD http://simbad.u-strasbg.fr/simbo.pl?bibcode=2023ApJ...951..102I
• NED https://ned.ipac.caltech.edu/uri/NED::InRefcode/2023ApJ...951..102I
• PREPRINT http://arxiv.org/abs/2206.04709
• ELECTR https://doi.org/10.3847%2F1538-4357%2Faccc87