NGC 6822 as a probe of dwarf galactic evolution
  NGC 6822 is the closest isolated dwarf irregular galaxy to the Milky Way. Its
proximity and stellar mass ($10^8 M_\odot$, large for a dwarf galaxy) allow for
a detailed study of its kinematic properties. The red giant branch (RGB) stars
at the galaxy's center are particularly interesting because they are aligned on
an axis perpendicular to the galaxy's more extended HI disk. We detected a
velocity gradient among the RGB population using spectra from Keck DEIMOS. This
rotation is aligned with the HI disk, but the sense of rotation is about the
major axis of the central RGB population. We measured the rotation velocity
($v$) and velocity dispersion ($\sigma$) of the RGB population in five
metallicity bins. We found an increase of rotation support ($v/\sigma$) with
increasing metallicity, driven primarily by decreasing dispersion. We also
deduced an increasing radial distance for lower metallicity stars at
$-0.5$~kpc/dex by relating the observed stellar kinematics to position via NGC
6822's HI velocity curve. While the inverted metallicity gradient-like could be
interpreted as evidence for an outside-in formation scenario, it may instead
indicate that stellar feedback disturbed a centrally star forming galaxy over
time.
