The Vc − σ0 relation of galaxies

Courteau et al. (2007a) reported on the dependence of the ratio of a galaxy's maximum circular velocity, V_c, to its central velocity dispersion, σ₀, on morphology, or equivalently total light concentration. This V_c − σ₀-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 V_c − σ₀ relation and its various dependences, they must simultaneously match other fundamental scaling relations such as the velocity-size-luminosity and color-luminosity relations. We focus here on the interpretation of parameters that enter the V_c − σ₀ relation to enable proper data-model comparisons and follow-up studies by galaxy modelers and observers.