Is dark matter essential for understanding galaxy interactions in clusters?

[twinsen]

Is dark matter required to explain the forces between galaxies or is it purely on a galactic scale.
Have there been any measures on dark matter in galactic clusters. Does M31 get influenced by dark matter in the milky way or does the visble matter in the milky way supply the required force to explain the movement of m31?

Alex

 

[cadnr]

I'm far from an expert in this area, but I think that a significant amount of evidence for dark matter comes from the analysis of the motion of galaxies in clusters.

I don't know anything about the M31-MW orbit, but I know that the LMC and SMC orbits are explained based on the Milky Way having a large dark matter halo.

 

[smallphi]

The first hystorical clue for dark matter was found by Fritz Zwicky in 1933 by observations of the Coma galactic cluster. The rotation curves of spiral galaxies came later. Current observations that actually measure the distribution of gravitating matter (most of which seems dark) in clusters are based on X-ray studies of the cluster gas or graviational lensing.

If you want to be well informed about the history and contemporary research in dark matter/energy, I suggest reading "Dark Side of the Universe" by Iain Nicolson. It's without formulas but gives a very good account on the history of the subject and all contemporary collaborations working in that field, even future experiments planned.

 

[mikehibbert]

Funnily enough I've just started a lecture course on this very topic!
...and cadnr, the evidence for dark matter does indeed come from analyzing motion of galaxies in clusters.

I don't think dark matter can actually be used in calculations yet because no-one actually knows what it is.

I believe it is theorized that dark matter (hence dark energy) is the reason the expansion of the universe is accelerating and not a constant expansion.