Originally Posted by matt.o

Nereid, there have been studies done searching for cluster rotation, most recently this one. The results are tentative, though they find evidence for 12 clusters which are rotating (and don't exhibit substructure). I think other methods have detected bulk motions in the intra cluster medium, not sure if it was net rotation.

I think both you and I know Jerry meant to refer to the dispersion of peculiar velocities of cluster galaxies (which is different from cluster rotation, Jerry).