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 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 H i stripped from the parent galaxies and within the extended dark matter halo of one of the parents as proposed by \citep bournaud03 , duc04 .