  Courteau et al. (2007a) reported on the dependence of the ratio of a galaxy's
maximum circular velocity, Vcirc, to its central velocity dispersion, sigma0,
on morphology, or equivalently total light concentration. This Vcirc-sigma0
concentration relation, which involves details about the local and global
galaxy physics, poses a fundamental challenge for galaxy structure models.
Furthermore, not only must these models reproduce the Vcirc-sigma0 relation and
its various dependences, they must simultaneously match other fundamental
scaling relations such as the velocity-size-luminosity and color-luminosity
relations of galaxies. We focus here on the interpretation of parameters that
enter the Vcirc-sigma0 relation to enable proper data-model comparisons and
follow-up studies by galaxy modelers and observers.
