Chemical abundance patterns in the inner Galaxy: the Scutum Red
  Supergiant Clusters
  The location of the Scutum Red-Supergiant (RSG) clusters at the end of the
Galactic Bar makes them an excellent probe of the Galaxy's secular evolution;
while the clusters themselves are ideal testbeds in which to study the
predictions of stellar evolutionary theory. To this end, we present a study of
the RSGs' surface abundances using a combination of high-resolution H-band
spectroscopy and spectral synthesis analysis. We provide abundance measurements
for elements C, O, Si, Mg, Ti, and Fe. We find that the surface abundances of
the stars studied are consistent with CNO burning and deep, rotationally
enhanced mixing. The average a/Fe ratios of the clusters are solar, consistent
with a thin-disk population. However, we find significantly sub-solar Fe/H
ratios for each cluster, a result which strongly contradicts a simple
extrapolation of the Galactic metallicity gradient to lower Galacto-centric
distances. We suggest that a simple one-dimensional parameterization of the
Galaxy's abundance patterns is insufficient at low Galactocentric distances, as
large azimuthal variations may be present. Indeed, we show that the abundances
of O, Si and Mg are consistent with independent measurements of objects in
similar locations in the Galaxy. In combining our results with other data in
the literature, we present evidence for large-scale (~kpc) azimuthal variations
in abundances at Galacto-centric distances of 3-5kpc. While we cannot rule-out
that this observed behaviour is due to systematic offsets between different
measurement techniques, we do find evidence for similar behaviour in a study of
the barred-spiral galaxy NGC4736 which uses homogeneous methodology. We suggest
that these azimuthal abundance variations could result from the intense but
patchy star formation driven by the potential of the central bar.
