Dynamical and photometric imprints of feedback processes on the early evolution of E/S0 galaxies

Abstract

We show that the observed Velocity Dispersion Function of E/S0 galaxies matches strikingly well the distribution function of virial velocities of massive halos virializing at z > 1.5, as predicted by the standard hierarchical clustering scenario in a \LambdaCDM cosmology, for a constant ratio sigma/V_vir = 0.55 \pm 0.05, close to the value expected at virialization if it typically occurred at z > 3. This strongly suggests that dissipative processes and later merging events had little impact on the matter density profile. Adopting the above sigma/V_vir ratio, the observed relationships between photometric and dynamical properties which define the fundamental plane of elliptical galaxies, such as the luminosity-sigma (Faber-Jackson) and the luminosity-effective radius relations, as well as the M_BH-sigma relation, are nicely reproduced. Their shapes turn out to be determined by the mutual feedback of star-formation (and supernova explosions)and nuclear activity, along the lines discussed by Granato et al. (2004). To our knowledge, this is the first semi-analytic model for which simultaneous fits of the fundamental plane relations and of the epoch-dependent luminosity function of spheroidal galaxies have been presented.