Tully-Fisher relation
An observed relation between the luminosity
of spiral galaxies and their maximum rotation
velocity. The Tully-Fisher relation is used as a way of estimating distances
to spirals. The form is a linear relation between the absolute
magnitude of a galaxy and the logarithm of the velocity at the flat
part of the rotation curve, although the slopes and intercepts of these
relations are different for Sa, Sb, and Sc type galaxies. Approximations
made in deriving the relation are that the mass-to-light ratios are constant
for all galaxies and that the average surface brightness of all galaxies
is also equal.
Related category
• GALAXIES
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