The Astrophysical Journal (Jan 2024)

EMPRESS. XII. Statistics on the Dynamics and Gas Mass Fraction of Extremely Metal-poor Galaxies

  • Yi Xu,
  • Masami Ouchi,
  • Yuki Isobe,
  • Kimihiko Nakajima,
  • Shinobu Ozaki,
  • Nicolas F. Bouché,
  • John H. Wise,
  • Eric 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 K. 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

DOI
https://doi.org/10.3847/1538-4357/ad06ab
Journal volume & issue
Vol. 961, no. 1
p. 49

Abstract

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We present the demography of the dynamics and gas mass fraction of 33 extremely metal-poor galaxies (EMPGs) with metallicities of 0.015–0.195 Z _⊙ and low stellar masses of 10 ^4 –10 ^8 M _⊙ in the local universe. We conduct deep optical integral field spectroscopy (IFS) for the low-mass EMPGs with the medium-high resolution ( R = 7500) grism of the 8 m Subaru FOCAS IFU instrument by the EMPRESS 3D survey, and investigate the H α emission of the EMPGs. Exploiting the resolution high enough for the low-mass galaxies, we derive gas dynamics with the H α lines by the fitting of three-dimensional disk models. We obtain an average maximum rotation velocity ( v _rot ) of 15 ± 3 km s ^−1 and an average intrinsic velocity dispersion ( σ _0 ) of 27 ± 10 km s ^−1 for 15 spatially resolved EMPGs out of 33 EMPGs, and find that all 15 EMPGs have v _rot / σ _0 < 1 suggesting dispersion-dominated systems. There is a clear decreasing trend of v _rot / σ _0 with the decreasing stellar mass and metallicity. We derive the gas mass fraction ( f _gas ) for all 33 EMPGs, and find no clear dependence on stellar mass and metallicity. These v _rot / σ _0 and f _gas trends should be compared with young high- z galaxies observed by the forthcoming JWST IFS programs to understand the physical origins of the EMPGs in the local universe.

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