Marsfield Lecture Theatre

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

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.