Elemental Abundances in M31: Iron and Alpha Element Abundances in M31's
  Outer Halo
  We present [Fe/H] and [$\alpha$/Fe] abundances, derived using spectral
synthesis techniques, for stars in M31's outer stellar halo. The 21 [Fe/H]
measurements and 7 [$\alpha$/Fe] measurements are drawn from fields ranging
from 43 to 165 kpc in projected distance from M31. We combine our measurements
with existing literature measurements, and compare the resulting sample of 23
stars with [Fe/H] and 9 stars with [$\alpha$/Fe] measurements in M31's outer
halo with [$\alpha$/Fe] and [Fe/H] measurements, also derived from spectral
synthesis, in M31's inner stellar halo ($r < $26 kpc) and dSph galaxies. The
stars in M31's outer halo have [$\alpha$/Fe] patterns that are consistent with
the largest of M31's dSph satellites (And I and And VII). These abundances
provide tentative evidence that the [$\alpha$/Fe] abundances of stars in M31's
outer halo are more similar to the abundances of Milky Way halo stars than to
the abundances of stars in M31's inner halo. We also compare the spectral
synthesis-based [Fe/H] measurements of stars in M31's halo with previous
photometric [Fe/H] estimates, as a function of projected distance from M31. The
spectral synthesis-based [Fe/H] measurements are consistent with a large-scale
metallicity gradient previously observed in M31's stellar halo to projected
distances as large as 100 kpc.
