The Vcirc-sigma0 Relation of Galaxies

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.