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

January 2024 • 2024ApJ...961...49X

Authors • Xu, Yi • Ouchi, Masami • Isobe, Yuki • Nakajima, Kimihiko • Ozaki, Shinobu • Bouché, Nicolas F. • Wise, John H. • 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 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 10⁴-10⁸ 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 Hα emission of the EMPGs. Exploiting the resolution high enough for the low-mass galaxies, we derive gas dynamics with the Hα 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.

Links

• SIMBAD http://simbad.u-strasbg.fr/simbo.pl?bibcode=2024ApJ...961...49X
• NED https://ned.ipac.caltech.edu/uri/NED::InRefcode/2024ApJ...961...49X
• PREPRINT http://arxiv.org/abs/2303.12467
• ELECTR https://doi.org/10.3847%2F1538-4357%2Fad06ab