Might black hole distribution at the center be a cause or effect its overall form? One might ignorantly surmise that elliptical galaxies have a single central black hole, spiral galaxies two, some irregulars have more (or none).

--I do not know. It looks like all(?) galaxies have a giant black hole. This suggests that they are important either in helping galaxy form, or in keeping it stable preventing it from self-destructing. The fact (if it is a fact) that Milky Way has a second big hole may or may not matter much. I'd guess "doesn't matter" since it is about 40 times lighter than the Big One and pretty near to it. The enormous energy releases occurring during the formation of the giant holes ("quasars") may have been important for purposes like keeping galaxies separated and ionizing gas. There has been some speculation that in the future, when Andromeda and the Milky Way probably will merge, their big holes may once again light up as quasars, outshining the whole rest of the galaxy. -- Warren D. Smith http://RangeVoting.org <-- add your endorsement (by clicking "endorse" as 1st step)