C. Mendes de Olivera on "Fossil and Compact Groups"
More than half of all galaxies come in groups, so does our Milky Way which resides in the ingeniously named "Local Group". But only a small fratction lives in compact groups. These groups are so close that they can share a common gas reservoir that has already merged while the optically visible galaxies still are individuals.
The most famous example is Stephan's Quintet and some details are given about it in this talk. In the tidal tails that are formed in interactions of galaxies, new dwarf galaxies can form and they are therefore called tidal-dwarf-galaxies.
She continues to present kinematical data from the same instrument that I used for "my galaxies" (CIGALE, a Marseille-based Fabry-Perot interferometer) and warns people to draw conclusions from long-slit spectra and low-resolution data from far-away galaxies, because the movements often show irreularities that only are revealed by 2D-velocity fields.