How does a dark matter halo outside a galaxy help to explain a galaxy rotation curve? Suppose for simplicity we use a model of a star rotating about a more massive star in a fixed circular orbit. For ...
What makes the stars that are farther from the nucleus of the galaxy go faster than those in the middle?
It has no sense that stars that have a bigger radius and apparently less angular speed($\omega$) goes faster than the ones near the center.
It seems that we know the rotation curve inside the sun's galactic orbit fairly accurately. Then wouldn't we be able to just take the derivative* of this to get the DM density profile at smaller ...