Revisiting the Giant Radio Galaxy ESO 422-G028: Part I. Discovery of a
  neutral inflow and recent star formation in a restarted giant
  Giant radio galaxies provide important clues into the life cycles and
triggering mechanisms of radio jets. With large-scale jets spanning 1.8 Mpc,
ESO 422-G028 ($z = 0.038$) is a giant radio galaxy that also exhibits signs of
restarted jet activity in the form of pc-scale jets. We present a study of the
spatially-resolved stellar and gas properties of ESO 422-G028 using optical
integral field spectroscopy from the WiFeS spectrograph. In addition to the
majority $\sim 13\,\rm Gyr$ old stellar population, ESO 422-G028 exhibits a
much younger ($\lesssim 10\,\rm Myr$ old) component with an estimated mass of $
10^{7.6}\,\rm M_\odot$ which is predominantly located in the North-West region
of the galaxy. Unusually, the ionised gas kinematics reveal two distinct disks
traced by narrow ($\sigma_{\rm H\alpha} < 100 \,\rm km\,s^{-1}$) and broad
($\sigma_{\rm H\alpha} > 150 \,\rm km\,s^{-1}$) H$\alpha$ emission
respectively. Both ionised gas disks are misaligned with the axis of stellar
rotation, suggesting an external origin. This is consistent with the prominent
interstellar Na D absorption, which traces a $1 - 3 \,\rm M_\odot \, yr^{-1}$
inflow of neutral gas from the North. We posit that an inflow of gas - either
from an accretion event or a gas-rich merger - has triggered both the starburst
and the restarted jet activity, and that ESO 422-G028 is potentially on the
brink of an epoch of powerful AGN activity.
