Exploring Chemical Homogeneity in Dwarf Galaxies: A VLT-MUSE study of
  JKB 18
  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$\pm$0.2
(~0.08 Zsol). Using high spatial-resolution integral field spectroscopy of the
entire system, we calculate chemical abundances for individual HII regions
using the direct method and derive oxygen abundance maps using strong-line
metallicity diagnostics. With large-scale dispersions in O/H, N/H and N/O of
~0.5-0.6 dex and regions harbouring chemical abundances outside this 1$\sigma$
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 timescales,
or self-enrichment from Wolf-Rayet stars are accountable. Using a galaxy-scale,
multi-phase, 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.
