How must the density of the dark matter halo change moving outward to produce a flat rotation curve?

Answer

It decreases outward at a rate that perfectly compensates for thinning visible matter

The flat rotation curve results because the density of the invisible dark matter halo thins out at just the right rate to balance the thinning visible stellar disk, keeping the speed constant.

How must the density of the dark matter halo change moving outward to produce a flat rotation curve?

#Videos

The Fastest Spinning Galaxy | Space is Weird - YouTube

galaxygalaxiesastronomySpinspiral galaxiesrotation speed