B?rbel Koribalski ( ATNF ) . ... The Grus-Quartet consists of four large spiral galaxies which are so close to each other that they should be interacting. The high starburst activity of two of the members, namely NGC 7552 and NGC 7582, is also thought to arise from tidal galaxy-galaxy interactions and subsequent formation of a bar in the disk. ... The colour gradient is in units of Jansky/beam km/s.) . The colour gradient is in units of km/s.) . ... Baerbel.Koribalski @ csiro.au ...