  We report on a study of the parameters characterizing the mass and velocity
distributions of two samples of relaxed elliptical-like objects (ELOs)
identified, at z=0, in a set of self-consistent hydrodynamical simulations
operating in the context of a concordance cosmological model. Star formation
(SF) has been phenomenologically implemented in the simulations in the
framework of the turbulent sequential scenario through a threshold gas density
and an efficiency parameter. Each ELO sample is characterized by the values
these parameters take. We have found that the (logarithms of the) ELO stellar
masses, projected stellar half-mass radii, and stellar central line-of-sight
(LOS) velocity dispersions define dynamical fundamental planes (FPs). Zero
points depend on the particular values that the SF parameters take, while
slopes do not change. The ELO samples have been found to show systematic trends
with the mass scale in both the relative content and the relative distributions
of the baryonic and the dark mass ELO components. The physical origin of these
trends lies in the systematic decrease, with increasing ELO mass, of the
relative dissipation experienced by the baryonic mass component along ELO mass
assembly, resulting in a tilt of the dynamical FP relative to the virial plane.
The dynamical FPs shown by the two ELO samples are consistent with that shown
by the SDSS elliptical sample in the same variables, with no further need for
any relevant contribution from stellar population effects to explain the
observed tilt. These effects could, however, have contributed to the scatter of
the observed FP, as the dynamical FPs have been found to be thinner than the
observed one. The results we report on hint, for the first time, at a possible
way to understand the tilt of the observed FP in a cosmological context.
