Mild Velocity Dispersion Evolution of Spheroid-like Massive Galaxies
  since z~2
  Making use of public spectra from Cimatti et al (2008), we measure for the
first time the velocity dispersion of spheroid-like massive (M_star ~ 10^11
M_sun) galaxies at z ~ 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 ~240 km/s at z ~ 1.6 down to ~180 km/s at z ~ 0.
Such mild evolution contrasts with the strong change in size (a factor of ~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.
