Arp 202: a TDG formed in a parent's extended dark matter halo?
  We report on H${\alpha}$ + [NII] imaging of the Arp 202 interacting pair and
its tidal dwarf galaxy (TDG) candidate as well as a GMOS long slit spectrum
from the TDG candidate, observed with the Gemini North telescope. Our
H${\alpha}$ + [NII] imaging reveals the TDG to have an elongated structure,
$\sim$ 1.9 kpc in length with the two principal star forming knots at either
end. Our observations also show the TDG candidate has a recessional
V$_{H\alpha}$ $\sim$ 3032 km s$^{-1}$, within 100 km s$^{-1}$ of the parent
pair's mean velocity and an oxygen abundance of 12+log(O/H) = 8.10$\pm$0.41.
The TDG's oxygen abundance is in good agreement with that of a star forming
region in NGC 2719A, one of the parent galaxies, which has an estimated oxygen
abundance of 12+log(O/H) = 8.05$\pm$0.41. The TDG's V$_{H\alpha}$ and oxygen
abundance confirm previous results validating the candidate as a TDG. The
absence of detectable emission from the TDG in $\textit{Spitzer}$ 3.6 $\mu$m
and 4.5 $\mu$m images together with the lack of absorption lines and weak
continuum in the spectrum is consistent with absence of an old population
($\gtrsim$ 0.5 Gyr). The location of the TDG within the interaction debris and
the absence of indicators of an old stellar population in the TDG are
consistent with a scenario in which the TDG is formed from HI stripped from the
parent galaxies and within the extended dark matter halo of one of the parents
as proposed by (Bournaud et al. 2003; Duc et al. 2004).
