|18th of November 2015|
|The frequency and properties of young tidal dwarf galaxies in nearby gas-rich groups|
|by Karen Lee-Waddell (CASS)|
|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.
Image caption: 3-colour composite CFHT MegaCam image of the central region of the NGC 3166/9 group (Lee-Waddell et al.)