MILD VELOCITY DISPERSION EVOLUTION OF SPHEROID-LIKE MASSIVE GALAXIES SINCE z ∼ 2

Making use of public spectra from Cimatti et al., we measure for the first time the velocity dispersion of spheroid-like massive (M* similar to 10(11) M-circle dot) galaxies at z similar to 1.6. By comparing with galaxies of similar stellar mass at lower redshifts, we find evidence for a mild evolution in velocity dispersion, decreasing from similar to 240 km s(-1) at z similar to 1.6 down to similar to 180 km s(-1) at z similar to 0. Such mild evolution contrasts with the strong change in size ( a factor of similar to 4) found for these type of objects in the same cosmic time, and it is consistent with a progressive larger role, at lower redshift, of the dark matter halo in setting the velocity dispersion of these galaxies. We discuss the implications of our results within the context of different scenarios proposed for the evolution of these massive objects.