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?

We present kinematics of six 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 & SIM; 7500) 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 substructures originating by inflow and/or outflow, we fit three-dimensional disk models to the observed H & alpha; 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 (& sigma; (0)) of 17-31 km s(-1), indicating dispersion-dominated (v (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 (gas) & SIME; 0.9-1.0. Comparing our results with other H & alpha; kinematics studies, we find that v (rot)/& sigma; (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 & 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 observations at z & SIM; 7.