We have redefined group membership of six southern galaxy groups in the local universe (mean cz < 2000 km s-1) based on new redshift measurements from our recently acquired Anglo-Australian Telescope 2dF spectra. For each group, we investigate member galaxy kinematics, substructure, luminosity functions and luminosity-weighted dynamics. Our calculations confirm that the group sizes, virial masses and luminosities cover the range expected for galaxy groups, except that the luminosity of NGC4038 is boosted by the central starburst merger pair. We find that a combination of kinematical, substructural and dynamical techniques can reliably distinguish loose, unvirialized groups from compact, dynamically relaxed groups. Applying these techniques, we find that Dorado, NGC4038 and NGC4697 are unvirialized, whereas NGC681, NGC1400 and NGC5084 are dynamically relaxed.
Monthly Notices of the Royal Astronomical Society
- Pub Date:
- November 2006
- galaxies: distances and redshifts;
- galaxies: kinematics and dynamics;
- 15 pages, 5 figures. Accepted for publication in MNRAS. Corrected F&