Subaru/FOCAS IFU revealed the metallicity gradient of a local extremely metal-poor galaxy

Yuri Kashiwagi*, Akio K. Inoue, Yuki Isobe, Kimihiko Nakajima, Masami Ouchi, Shinobu Ozaki, Seiji Fujimoto, Yoshiaki Ono, Takashi Kojima

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review


We present the first measurement of the metallicity gradient in extremely metal-poor galaxies (EMPGs). With Subaru/Faint Object Camera And Spectrograph (FOCAS) Integral Field Unit (IFU), we have observed a nearby, low-mass EMPG, HSC J1631+4426, whose oxygen abundance and stellar mass are known to be 12 + log (O/H) = 6.9 and log10(M∗/M⊙) = 5.8, respectively. The measured metallicity gradient is -0.36 ± 0.04 dex kpc-1 corresponding to -0.049 ± 0.006 dex R-1e for the continuum effective radius of Re = 0.14 kpc. Our observation has successfully demonstrated that threedimensional spectroscopy with 8m-class telescopes is powerful enough to reveal the metallicity distribution in local EMPGs, providing precious information on the baryon cycle in local analogs of primordial galaxies in the early Universe.

Original languageEnglish
Pages (from-to)1631-1637
Number of pages7
JournalPublications of the Astronomical Society of Japan
Issue number6
Publication statusPublished - 2021 Dec 1


  • galaxies: ISM
  • galaxies: abundances
  • galaxies: dwarf
  • galaxies: evolution
  • galaxies: individual (HSC J1631+4426)

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science


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