Exploring chemical homogeneity in dwarf galaxies: A VLT-MUSE study of JKB 18

Bethan L. James, Nimisha Kumari, Andrew Emerick, Sergey E. Koposov, Kristen B.W. McQuinn, Daniel P. Stark, Vasily Belokurov, Roberto Maiolino

Research output: Contribution to journalArticlepeer-review

Abstract

Deciphering the distribution of metals throughout galaxies is fundamental in our understanding of galaxy evolution. Nearby, low-metallicity, star-forming dwarf galaxies, in particular, can offer detailed insight into the metal-dependent processes that may have occurred within galaxies in the early Universe. Here, we present VLT/MUSE observations of one such system, JKB 18, a blue diffuse dwarf galaxy with a metallicity of only 12 + log(O/H)=7.6 ± 0.2 (∼0.08 Z⊠). Using high spatial resolution integral-field spectroscopy of the entire system, we calculate chemical abundances for individual H ii regions using the direct method and derive oxygen abundance maps using strong-line metallicity diagnostics. With large-scale dispersions in O/H, N/H, and N/O of ∼0.5-0.6 dex and regions harbouring chemical abundances outside this 1σ distribution, we deem JKB 18 to be chemically inhomogeneous. We explore this finding in the context of other chemically inhomogeneous dwarf galaxies and conclude that neither the accretion of metal-poor gas, short mixing time-scales or self-enrichment from Wolf-Rayet stars are accountable. Using a galaxy-scale, multiphase, hydrodynamical simulation of a low-mass dwarf galaxy, we find that chemical inhomogeneities of this level may be attributable to the removal of gas via supernovae and the specific timing of the observations with respect to star formation activity. This study not only draws attention to the fact that dwarf galaxies can be chemically inhomogeneous, but also that the methods used in the assessment of this characteristic can be subject to bias.

Original languageEnglish (US)
Pages (from-to)2564-2581
Number of pages18
JournalMonthly Notices of the Royal Astronomical Society
Volume495
Issue number3
DOIs
StatePublished - May 14 2020

Keywords

  • galaxies: Abundances
  • galaxies: dwarf
  • galaxies: evolution
  • galaxies: irregular
  • galaxies: star formation

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science

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