Tully-Fisher Relation

• Pros:

• applicable to ~200Mpc

• spiral galaxies found in clusters, as well as in field (most widely used secondary distance indicator)

• Cons:

• dispersion is rather large (intrinsic s~0.25 mag, which corresponds to 12% in distance); need to observe 10-15 galaxies per cluster

• before the launch of HST, only a handful of calibrators were available

• no theoretical proof

Notes: