C. Sengupta, T. C. Scott, S. Paudel, K. S. Dwarakanath, D. J. Saikia, B. W. Sohn
Abstract
We present results from our Giant Metrewave Radio Telescope (GMRT) H I observations of the Arp 305 system. The system consists of two interacting spiral galaxies NGC 4016 and NGC 4017, a large amount of resultant tidal debris and a prominent tidal dwarf galaxy (TDG) candidate projected within the tidal bridge between the two principal galaxies. Our higher resolution GMRT H I mapping, compared to previous observations, allowed detailed study of smaller scale features. Our H I analysis supports the conclusion in Hancock et al. that the most recent encounter between the pair occurred ∼4×108 yr ago. The GMRT observations also show H I features near NGC 4017 that may be remnants of an earlier encounter between the two galaxies. The H I properties of the bridge TDG candidate include MHi∼6.6×108 M⊙ and VHi=3500±7 km s−1, which are in good agreement with the velocities of the parent galaxies. Additionally, the TDG's H I linewidth of 30 km s−1 and modest velocity gradient together with its star formation rate of 0.2 M⊙ yr−1 add to the evidence favouring the bridge candidate being a genuine TDG. The bridge TDG's Spitzer 3.6 and 4.5 μm counterparts with a [3.6]−[4.5] colour ∼ −0.2 mag suggests that stellar debris may have seeded its formation. Future spectroscopic observations could confirm this formation scenario and provide the metallicity, which is a key criterion for the validation of TDG candidates.
Keywords
galaxies: dwarf; galaxies: individual: Arp 305; galaxies: interactions; galaxies: spiral; galaxies: star formation
Monthly Notices of the Royal Astronomical Society
Volume 469, Issue 3, Page 12
2017 August