The Abundance Gradient in the Extremely Faint Outer Disk of NGC 300
  In earlier work, we showed for the first time that the resolved stellar disk
of NGC 300 is very extended with no evidence for truncation, a phenomenon that
has since been observed in other disk galaxies. We revisit the outer disk of
NGC 300 in order to determine the metallicity of the faint stellar population.
With the GMOS camera at Gemini South, we reach 50% completeness at (g',
i')=(26.8-27.4,26.1-27.0) in photometric conditions and 0.7" seeing. At these
faint depths, careful consideration must be given to the background galaxy
population. The mean colors of the outer disk stars fall within the spread of
colors for the background galaxies, but the stellar density dominates the
background galaxies by ~2:1. The predominantly old stellar population in the
outer disk exhibits a negative abundance gradient - as expected from models of
galaxy evolution - out to about 10 kpc where the abundance trend changes sign.
We present two scenarios to explain the flattening, or upturn, in the
metallicity gradient of NGC 300 and discuss the implication this has for the
broader picture of galaxy formation.
