The Young Outer Disk of M83
  Deep near-infrared images recorded with NICI on Gemini South are used to
investigate the evolved stellar content in the outer regions of the south east
quadrant of the spiral galaxy M83. A diffuse population of asymptotic giant
branch (AGB) stars is detected outside of the previously identified young and
intermediate age star clusters in the outer disk. The brightest AGB stars have
M_K > -8, and the AGB luminosity function (LF) is well-matched by model LFs
that assume ages < 1 Gyr. The specific star formation rate (SFR) during the
past few Gyr estimated from AGB star counts is consistent with that computed
from mid-infrared observations of star clusters at similar radii, and it is
concluded that the disruption timescale for star clusters in the outer disk is
<< 1 Gyr. The luminosity function and specific frequency of AGB stars varies
with radius, in a manner that is indicative of lower luminosity-weighted ages
at larger radii. Modest numbers of red supergiants are also found, indicating
that there has been star formation during the past 100 Myr, while the ratio of
C stars to M giants is consistent with that expected for a solar metallicity
system that has experienced a constant SFR for the past few Gyrs.
