HI, star formation and tidal dwarf candidate in the Arp 305 system
  We present results from our Giant Metrewave Radio Telescope (GMRT) HI
observations of the Arp 305 system. The system consists of two interacting
spiral galaxies NGC 4016 and NGC 4017, a large amount of resultant tidal debris
and a prominent tidal dwarf galaxy (TDG) candidate projected within the tidal
bridge between the two principal galaxies. Our higher resolution GMRT HI
mapping, compared to previous observations, allowed detailed study of smaller
scale features. Our HI analysis supports the conclusion in Hancock et al.
(2009) that the most recent encounter between the pair occurred $\sim$ 4
$\times$ 10$^8$ yrs ago. The GMRT observations also show HI features near NGC
4017 which may be remnants of an earlier encounter between the two galaxies.
The HI properties of the Bridge TDG candidate include: M(HI) $\sim$ 6.6
$\times$ 10$^8$ msolar and V(HI) = 3500$\pm$ 7 km/s, which is in good agreement
with the velocities of the parent galaxies. Additionally the TDG's HI linewidth
of 30 km/s and a modest velocity gradient together with its SFR of 0.2
msolar/yr add to the evidence favouring the bridge candidate being a genuine
TDG. The Bridge TDG's \textit{Spitzer} 3.6 $\mu$m and 4.5 $\mu$m counterparts
with a [3.6]--[4.5] colour $\sim$ -0.2 mag suggests stellar debris may have
seeded its formation. Future spectroscopic observations could confirm this
formation scenario and provide the metallicity which is a key criteria for the
validation for TDG candidates.
