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Spiral Galaxies must have a great deal more mass than elliptical galaxies of the same size in order to account for the flat velocity curve. I've seen references of eight to ten times the visible mass. So then Spiral Galaxies should act as much better gravity lenses than an elliptical (of the same size). Do we have any evidence either for or against the Dark Matter in Spiral Galaxies acting as stronger gravity lenses than their elliptical counterparts?

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The problem is that galaxies come in all sorts of sizes and therefore with different lensing strengths. The experiment would be to measure the lensing of elliptical galaxies then compare this with their mass and see if the lensing looks bigger than the observed mass would suggest.

The trouble is that while lensing measurements give us the total mass it's difficult to get a good measure for the mass of the normal matter alone in elliptical galaxies. Various attempts to do this have been reported. A quick Google found me The stellar and dark matter distributions in elliptical galaxies from the ensemble of strong gravitational lenses (nice concise title :-).

It does seem that elliptical galaxies do have less dark matter than spiral galaxies, though the experimental constraints are still rather poor. In some special cases, such as M87, the presence of dark matter has been inferred from the dynamics, but again the errors are still large.

There is quite a nice article on this subject on the Astrobites website.

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  • $\begingroup$ Thanks for the response. I've scoured the web and it appears that there's been work done and the evidence for Dark Matter in elliptical galaxies is tenuous at best. My question is really in regard to spirals. Since they require more Dark Matter to flatten out the velocity profile, they should make better lenses. What evidence do we have that shows Spiral Galaxies acting like gravity lenses. I'm having trouble finding any. $\endgroup$ – Quarkly Sep 24 '14 at 10:30

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