HI in the Arp 202 system and its tidal dwarf candidate

TL;DR

This study uses GMRT HI observations to investigate the Arp 202 system, confirming a tidal dwarf galaxy candidate through its HI emission and linking it to galaxy interaction, while comparing its properties to other blue TDGs.

Contribution

First detailed GMRT HI analysis of Arp 202 confirming the tidal dwarf galaxy candidate and its association with galaxy interaction.

Findings

HI emission detected from the tidal tail and TDG candidate

HI and possibly stellar masses are similar to the lowest mass TDGs

Blue TDG candidates form a small, distinct subgroup with similar properties

Abstract

We present results from our Giant Metrewave Radio Telescope (GMRT) HI observations of the interacting pair Arp 202 (NGC 2719 and NGC 2719A). Earlier deep UV(GALEX) 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 HI emission from the Arp 202 system, including HI counterparts for the tidal tail and the TDG candidate. Our GMRT HI morphological and kinematic results clearly link the HI tidal tail and the HI 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 HI (and probably stellar) masses of this extremely blue group are similar to the lowest HI 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.