Changes

<math>A = k + 4 \times \ln v</math>

<math>A = k + 4 \times \ln v</math>

The Tully-Fisher relation was empirical, but Hartnett has given it a theoretical basis. Hartnett tested his equation against the observed values of circular velocity of tracer gases in object NGC 3198 as a function of radial distance from the center. He found that this equation fit the observations almost exactly, while a traditional Newtonian equation for radial velocity,

where A = absolute magnitude. The Tully-Fisher relation was empirical, but Hartnett has given it a theoretical basis. Furthermore, the M given in Hartnett's equation is the regular luminous mass and ''not'' a Newtonian dynamical mass. Hence, no correction for any dark-matter proportion is necessary.

 

Hartnett tested his equation against the observed values of circular velocity of tracer gases in object NGC 3198 as a function of radial distance from the center. He found that this equation fit the observations almost exactly, while a traditional Newtonian equation for radial velocity,

<math>v^2 = \frac{GM}{R}</math>

<math>v^2 = \frac{GM}{R}</math>