Portal de Periódicos da CAPES

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?

2023; IOP Publishing; Volume: 951; Issue: 2 Linguagem: Inglês

10.3847/1538-4357/accc87

1538-4357

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

Astrophysical Phenomena and Observations

We present kinematics of 6 local extremely metal-poor galaxies (EMPGs) with low metallicities ($0.016-0.098\ Z_{\odot}$) and low stellar masses ($10^{4.7}-10^{7.6} M_{\odot}$). Taking deep medium-high resolution ($R\sim7500$) integral-field spectra with 8.2-m Subaru, we resolve the small inner velocity gradients and dispersions of the EMPGs with H$\alpha$ emission. Carefully masking out sub-structures originated by inflow and/or outflow, we fit 3-dimensional disk models to the observed H$\alpha$ flux, velocity, and velocity-dispersion maps. All the EMPGs show rotational velocities ($v_{\rm rot}$) of 5--23 km s$^{-1}$ smaller than the velocity dispersions ($\sigma_{0}$) of 17--31 km s$^{-1}$, indicating dispersion-dominated ($v_{\rm rot}/\sigma_{0}=0.29-0.80<1$) 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 $f_{\rm gas}\simeq 0.9-1.0$. Comparing our results with other H$\alpha$ kinematics studies, we find that $v_{\rm rot}/\sigma_{0}$ decreases and $f_{\rm gas}$ increases with decreasing metallicity, decreasing stellar mass, and increasing specific star-formation rate. We also find that simulated high-$z$ ($z\sim 7$) 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 (JWST) observations at $z\sim 7$.