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