rtomes: Arp has reported galaxies that show discontinuities in their redshift profiles of 72 km/s. IMO this would happen when a galaxy is in the process of shifting from one state to the next and would be a bit like water freezing or something like that. It would begin somewhere and spread out as a wave, though there might be a few leaders and laggards. This data of Arp's is hard to explain any other way. Sorry, I do not have a reference for that.

Nereid: If you don't have a reference for it, what merit should this have, in any scientific investigation?

For example, I could claim that "[t]his data of Arp's" was all made up, late one evening after a too many pints at the local pub. Without a reference, how can anyone reading this decide, objectively, whose story is right?