The fate of high redshift massive compact galaxies in dense environments
  Massive compact galaxies seem to be more common at high redshift than in the
local universe, especially in denser environments. To investigate the fate of
such massive galaxies identified at z~2 we analyse the evolution of their
properties in three cosmological hydrodynamical simulations that form
virialised galaxy groups of mass ~10^13 Msun hosting a central massive
elliptical/S0 galaxy by redshift zero. We find that at redshift ~2 the
population of galaxies with M_*> 2 10^10 Msun is diverse in terms of mass,
velocity dispersion, star formation and effective radius, containing both very
compact and relatively extended objects. In each simulation all the compact
satellite galaxies have merged into the central galaxy by redshift 0 (with the
exception of one simulation where one of such satellite galaxy survives).
Satellites of similar mass at z = 0 are all less compact than their high
redshift counterparts. They form later than the galaxies in the z = 2 sample
and enter the group potential at z < 1, when dynamical friction times are
longer than the Hubble time. Also, by z = 0 the central galaxies have increased
substantially their characteristic radius via a combination of in situ star
formation and mergers. Hence in a group environment descendants of compact
galaxies either evolve towards larger sizes or they disappear before the
present time as a result of the environment in which they evolve. Since the
group-sized halos that we consider are representative of dense environments in
the LambdaCDM cosmology, we conclude that the majority of high redshift compact
massive galaxies do not survive until today as a result of the environment.
