EMPRESS. III. Morphology, stellar population, and dynamics of extremely metal-poor galaxies (EMPGs): Are EMPGs local analogs of high-z young galaxies?

Yuki Isobe, Masami Ouchi, Takashi Kojima, Takatoshi Shibuya, Kohei Hayashi, Michael Rauch, Shotaro Kikuchihara, Haibin Zhang, Yoshiaki Ono, Seiji Fujimoto, Yuichi Harikane, Ji Hoon Kim, Yutaka Komiyama, Haruka Kusakabe, Chien Hsiu Lee, Ken Mawatari, Masato Onodera, Yuma Sugahara, Kiyoto Yabe

Research output: Contribution to journalArticlepeer-review

Abstract

We present the morphology and stellar population of 27 extremely metal-poor galaxies (EMPGs) at z ∼ 0 with metallicities of 0.01–0.1 Ze. We conduct multicomponent surface brightness (SB) profile fitting for the deep Subaru/Hyper Suprime-Cam i-band images of the EMPGs with the GALFIT software, carefully removing the SB contributions of tails. We find that the EMPGs with a median stellar mass of log(M* M) = 6.0 have a median Sérsic index of n = 1.1 and a median effective radius of re = 200 pc, suggesting that typical EMPGs have a very compact disk. We compare the EMPGs with z ∼ 6 galaxies and local galaxies on the size–mass (re–M*) diagram, and identify that the majority of the EMPGs have an re–M* relation similar to z ∼ 0 star-forming galaxies rather than z ∼ 6 galaxies. Not every EMPG is a local analog of high-z young galaxies in the re–M* relation. A spectrum of one pair of EMPG and tail, so far available, indicates that the tail is dynamically related to the EMPG with a median velocity difference of ΔV = 101 ± 32 km s-1. This moderately large ΔV cannot be explained by the dynamics of the tail, but likely by the infall on the tail. For the first time, we may identify the metal-poor star-forming system just now infalling into the tail.

Original languageEnglish
Article number54
JournalAstrophysical Journal
Volume918
Issue number2
DOIs
Publication statusPublished - 2021 Sep 10

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science

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