In:
The Astrophysical Journal, American Astronomical Society, Vol. 951, No. 2 ( 2023-07-01), p. 102-
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 H α emission. Carefully masking out substructures originating by inflow and/or outflow, we fit three-dimensional disk models to the observed H α 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 H α 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.
Type of Medium:
Online Resource
ISSN:
0004-637X
,
1538-4357
DOI:
10.3847/1538-4357/accc87
Language:
Unknown
Publisher:
American Astronomical Society
Publication Date:
2023
detail.hit.zdb_id:
2207648-7
detail.hit.zdb_id:
1473835-1
SSG:
16,12
