The importance of dry and wet merging on the formation and evolution of elliptical galaxies

With the aid of a simple yet robust approach, we investigate the influence of dissipationless and dissipative merging on galaxy structure and the consequent effects on the scaling laws followed by elliptical galaxies. Our results suggest that elliptical galaxies cannot be originated by parabolic merging of low- mass spheroids only, even in the presence of substantial gas dissipation. However, we also found that scaling laws such as the Faber- Jackson, Kormendy, fundamental plane, and M-BH-sigma relations, when considered over the whole mass range spanned by elliptical galaxies in the local universe, are robust against merging. We conclude that galaxy scaling laws, possibly established at high redshift by the fast collapse in preexisting dark matter halos of gas- rich and clumpy stellar distributions, are compatible with a ( small) number of galaxy mergers at lower redshift.