14
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
