How are clusters of galaxies formed?

[exponent137]

Maybe I hear somewhere that grups of galaksies forms sphere.
Or maybe that groups of gropus of galaksies forms sphere.
How it is with this?

 

[Astronuc]

Here is a good overview of clusters of galaxies -

http://universe-review.ca/F04-galactic-cluster.htm

See Figure 04-05a Cluster of Galaxies Classification and related comments.

It is highly improbable that clusters of galaxies have been built up by chance encounters of galaxies in the general field. It just takes too long (longer than the age of the universe) to complete the process. Therefore, either that clusters are systems whose member galaxies became gravitationally bound at more or less the same time, or that the clusters represent condensations from pregalaxian material and that subcondensations within them became galaxies.

Another summary - http://csep10.phys.utk.edu/astr162/lect/gclusters/gclusters.html