Detecting metal-poor gas accretion in the star-forming dwarf galaxies UM
  461 and Mrk 600
  Using VIMOS-IFU observations, we study the interstellar medium (ISM) of two
star-forming dwarf galaxies, UM 461 and Mrk 600. Our aim was to search for the
existence of metallicity inhomogeneities that might arise from infall of nearly
pristine gas feeding ongoing localized star-formation. The IFU data allowed us
to study the impact of external gas accretion on the chemical evolution as well
as the ionised gas kinematics and morphologies of these galaxies. Both systems
show signs of morphological distortions, including cometary-like morphologies.
We analysed the spatial variation of 12 + log(O/H) abundances within both
galaxies using the direct method (T_e), the widely applied HII-CHI-mistry code,
as well as by employing different standard calibrations. For UM 461 our results
show that the ISM is fairly well mixed, at large scales, however we find an
off-centre and low-metallicity region with 12 + log(O/H) < 7.6 in the SW part
of the brightest HII region, using the direct method. This result is consistent
with the recent infall of a low mass metal-poor dwarf or HI cloud into the
region now exhibiting the lowest metallicity, which also displays localized
perturbed neutral and ionized gas kinematics. Mrk 600 in contrast, appears to
be chemically homogeneous on both large and small scales. The intrinsic
differences in the spatially resolved properties of the ISM in our analysed
galaxies are consistent with these systems being at different evolutionary
stages.
