Stellar Mass-to-Light Ratios and the Tully-Fisher relation
  We use spiral galaxy evolution models to argue that there are substantial variations in stellar mass-to-light ratio (M/L) within and among galaxies. Our models show a strong correlation between stellar M/L and galaxy color. We compare the colors and maximum-disk M/L values of a sample of galaxies to the model color-M/L relation, finding that a Salpeter IMF is too massive but that an IMF with fewer low mass stars fits the observations well. Applying our color-M/L relation to the Tully-Fisher (TF) relation, we find a stellar mass TF-relation that is independent of originating passband. Adding the HI gas mass, we find that the maximum slope of the baryonic TF-relation is 3.5. 
Roelof S.de Jong and Eric F. Bell (Steward Observatory)