Interacting system NGC 7805/6 (Arp 112) and its tidal dwarf galaxy
  candidate
  We present results from our Giant Metrewave Radio Telescope (GMRT) HI,
Himalayan Chandra Telescope (HCT) Halpha, 1m Sampurnanand Telescope (ST) and
1.3m Devasthal Fast Optical Telescope (DFOT) deep optical observations of NGC
7805/6 (Arp 112) system to test KUG 2359+311's tidal dwarf galaxy (TDG)
candidacy and explore the properties of the interacting system. Our GMRT HI map
shows no HI detection associated with KUG 2359+311, nor any HI tail or
bridge-like structure connecting KUG 2359+311 to the NGC 7805/6 system. Our HCT
Halpha image on the other hand, shows strong detections in KUG 2359+311, with
net SFR ~ 0.035$\pm 0.009 {\rm M}_{\odot}\,{\rm yr}^{-1}$. The Halpha data
constrains the redshift of KUG 2359+311 to $0.00 \le z \le 0.043$, compared to
the redshift of NGC 7806 of ~ 0.015. TDGs detected to date have all been HI
rich, and displayed HI, ionised gas and stellar tidal debris trails (bridges or
tails) linking them to their parent systems. But neither our HI data nor our
optical images, while three magnitudes deeper than SDSS, reveal tidal trail
connecting KUG 2359+311 to NGC 7805/6. Lack of HI , presence of an old stellar
population, ongoing star formation, reasonably high SFR compared to normal
dwarf galaxies suggest that KUG 2359+311 may not be an Arp 112 TDG. It is most
likely a case of a regular gas-rich dwarf galaxy undergoing a morphological
transformation after having lost its entire gas content to an interaction with
the Arp 112 system. Redshift and metallicity from future spectroscopic
observations of KUG 2359+311 would help clarify the nature of this enigmatic
structure.
