Figure 5

Figure 5: Residuals (δlog Vf) from the baryonic Tully–Fisher relation as a function of a galaxy’s characteristic baryonic surface density (Σb = 0.75Mb ∕R2p [271], Rp being the radius at which the contribution of baryons to the rotation curve peaks). Color differentiates between star (dark blue) and gas (light blue) dominated galaxies as in Figure 3, but not all galaxies there have sufficient data (especially of Rp) to plot here. Stellar masses have been estimated with stellar population synthesis models [42]. More accurate data, with uncertainty on rotation velocity less than 5%, are shown as larger points; less accurate data are shown as smaller points. The rotation velocity of galaxies shows no dependence on the distribution of baryons as measured by Σb or Rp. This is puzzling in the conventional context, where 2 V = GM ∕r should lead to a strong systematic residual [109].