The Comparative Chemical Evolution of an Isolated Dwarf Galaxy: A VLT
  and Keck Spectroscopic Survey of WLM
  Building on our previous spectroscopic and photometric analysis of the
isolated Local Group dwarf irregular (dIrr) galaxy WLM, we present a comparison
of the metallicities of its RGB stars with respect to the well studied Local
Group dwarf spheroidal galaxies (dSphs) and Magellanic Clouds. We calculate a
mean metallicity of [Fe/H]$ = -1.28 \pm 0.02$, and intrinsic spread in
metallicity of $\sigma = 0.38 \pm 0.04$ dex, similar to the mean and spread
observed in the massive dSph Fornax and the Small Magellanic Cloud. Thus,
despite its isolated environment the global metallicity still follows
expectations for WLM's mass and its global chemical evolution is similar to
other nearby luminous dwarf galaxies (gas-rich or gas-poor). The data also show
a radial gradient in [Fe/H] of $\rm{d[Fe/H]/dr_{c}} = -0.04 \pm 0.04$ dex
$\rm{r_{c}^{-1}}$, which is flatter than that seen in the unbiased and
spatially extended surveys of dSphs. Comparison of the spatial distribution of
[Fe/H] in WLM, the Magellanic Clouds, and a sample of Local Group dSphs, shows
an apparent dichotomy in the sense that the dIrrs have statistically flatter
radial [Fe/H] gradients than the low angular momentum dSphs. The correlation
between angular momentum and radial metallicity gradient is further supported
when considering the Local Group dEs. This chemodynamic relationship offers a
new and useful constraint for environment driven dwarf galaxy evolution models
in the Local Group.
