H I in the Arp 202 system and its tidal dwarf candidate

Abstract

We present results from our Giant Metrewave Radio Telescope (GMRT) H i observations of the interacting pair Arp 202 (NGC 2719 and NGC 2719A). Earlier deep ultraviolet (Galaxy Evolution Explorer) observations of this system revealed a tidal-tail-like extension with a diffuse object towards its end, proposed as a tidal dwarf galaxy (TDG) candidate. We detect H i emission from the Arp 202 system, including H i counterparts for the tidal tail and the TDG candidate. Our GMRT H i morphological and kinematic results clearly link the H i tidal tail and the H i TDG counterparts to the interaction between NGC 2719 and NGC 2719A, thus strengthening the case for the TDG. The Arp 202 TDG candidate belongs to a small group of TDG candidates with extremely blue colours. In order to gain a better understanding of this group we carried out a comparative study of their properties from the available data. We find that H i (and probably stellar) masses of this extremely blue group are similar to the lowest H i mass TDGs in the literature. However the number of such blue TDG candidates examined so far is too small to conclude whether or not their properties justify them to be considered as a subgroup of TDGs.