the spherical and disky components $M_{\rm bukge}/M_{\rm disk}$. A more observationally-friendly quantity to express this is the ratio between random and total motions. In the model this corresponds to $\sigma/V_{\rm C}$, where $\sigma$ is defined by Eq. (\[sigma\]), and $V_{\rm C}^2=\sigma^2+V_{\rm disk}^2$ (Eq. (\[Vc\])). The bulge and dark matter halo mostly contribute with velocity dispersion, and the disk mostly with rotation.

![image](f3.eps)

After splitting the model galaxies in photometric classes Sa, Sb and Sc, we consider the ratio $\sigma/V_{\rm C}$ for each type, and plot it in Fig. (\[sigmamodel\]), as a function of the total circular velocity $V_{\rm C}$, calculated at $2.2 \ R_{\rm D}$ (where $R_{\rm D}$ is defined by Eq. (\[rdafter\])); these are the *circles, colour-coded as in Fig. (\[tfmodel\])*. The model galaxies show a differentiation in $\sigma/V_{\rm C}$ depending on the B-band selected morphology, with later-type spirals showing a smaller total velocity dispersion than the earlier types, for a given total circular velocity, and a smaller scatter. This shows how dynamics and star formation history are interlinked in the model: the hierarchical build-up of galaxies grows bulges through mergers and evolves the star formation rates to produce redder early-type objects. Moreover, following the nature of hierarchical mass 