From galaxy-scale fueling to nuclear-scale feedback: the merger-state of
  radio galaxies 3C293, 3C305 & 4C12.50
  Powerful radio galaxies are often associated with gas-rich galaxy mergers.
These mergers may provide the fuel to trigger starburst and active galactic
nuclear (AGN) activity. In this Research Note, we study the host galaxies of
three seemingly young or re-started radio sources that drive fast outflows of
cool neutral hydrogen (HI) gas, namely 3C 293, 3C 305 and 4C 12.50 (PKS
1345+12). Our aim is to link the feedback processes in the central kpc-scale
region with new information on the distribution of stars and gas at scales of
the galaxy. For this, we use deep optical V-band imaging of the host galaxies,
complemented with HI emission-line observations to study their gaseous
environments. We find prominent optical tidal features in all three radio
galaxies, which confirm previous claims that 3C 293, 3C 305 and 4C 12.50 have
been involved in a recent galaxy merger or interaction. Our data show the
complex morphology of the host galaxies, and identify the companion galaxies
that are likely involved in the merger or interaction. The radio sources appear
to be (re-)triggered at a different stage of the merger; 4C 12.50 is a
pre-coalescent and possibly multiple merger, 3C 293 is a post-coalescent merger
that is undergoing a minor interaction with a close satellite galaxy, while 3C
305 appears to be shaped by an interaction with a gas-rich companion. For 3C
293 and 3C 305, we do not detect HI beyond the inner ~30-45 kpc region, which
shows that the bulk of the cold gas is concentrated within the host-galaxy,
rather than along the widespread tidal features.
