Australia Telescope National Facility

Karen Lee-Waddell Colloquium: The frequency and properties of young tidal dwarf galaxies in nearby gas-rich g

Marsfield Lecture Theatre

Abstract

Many galaxies reside in group environments where tidal interactions dominate the dynamics of the contained members. Gaseous material pulled from initial close encounters between galaxies can produce second-generation tidal dwarf galaxies (TDGs), which differ from first-generation `classical' dwarfs by their higher metal content and lack of dark matter. I present the results of a multi-wavelength investigation of the dwarf galaxy populations in three gas-rich interacting galaxy groups: NGC 871/7, NGC 3166/9, NGC 4725/47.

Using degree-scale Giant Metrewave Radio Telescope (GMRT) HI mosaics, deep optical photometry from the Canada-France-Hawaii Telescope (CFHT) and archival Galaxy Evolution Explorer (GALEX) imaging, we have measured the HI and stellar properties of the detectable gas-rich low-mass objects to robustly classify each one as a first-generation galaxy, a short-lived tidal knot or a TDG candidate. Our observations detect several classical dwarfs and various tidal knots in the three groups. We optimistically identify ~1 long-lived tidal object per interacting galaxy pair, implying that TDGs are not readily produced. The tidal objects examined in this small survey also appear to have a wider variety of properties than TDGs of similar mass formed in current simulations of interacting galaxies.