Spiral/Lenticular Galaxies
Tully-Fisher relation interpretation:
Assuming mass follows light, then
Then most mass within r ~ h and the maximum of
the rotation curve goes as the Keplerian velocity at
radius h.  Then making the same Newton/Kepler
argument:
Combine the equations to eliminate h and you get
that mass goes as Vmax4, and for spirals M/L is
roughly constant in the disk, so expect L ~ Vmax4