Tully–Fisher relation

In astronomy, the Tully–Fisher relation (TFR) is a widely verified empirical relationship between the mass or intrinsic luminosity of a spiral galaxy and its asymptotic rotation velocity or emission line width.

[5] Many values of the Hubble constant have been derived from Tully–Fisher analysis, starting with the first paper and continuing through 2024.

[1] Several different forms of the TFR exist, depending on which precise measures of mass, luminosity or rotation velocity one takes it to relate.

Tully and Fisher used optical luminosity, but subsequent work showed the relation to be tighter when defined using microwave to infrared (K band) radiation (a good proxy for stellar mass), and even tighter when luminosity is replaced by the galaxy's total stellar mass.

In Modified Newtonian dynamics (MOND), the BTFR (with power-law index exactly 4) is a direct consequence of the gravitational force law effective at low acceleration.