  The Fundamental Plane (FP) is an empirical relation between the size, surface
brightness, and velocity dispersion of early-type galaxies. This relation has
been studied extensively for early-type galaxies in the local universe to
constrain galaxy formation mechanisms. The evolution of the zeropoint of this
plane has been extended to high redshifts to study the luminosity evolution of
massive galaxies, under the assumption of structural homology. In this work, we
assess this assumption by replacing surface brightness with stellar mass
density and present the evolution of the "mass FP" for massive, quiescent
galaxies since z~2. By accounting for stellar populations, we thereby isolate
and trace structural and dynamical evolution. Despite the observed dramatic
evolution in the sizes and morphologies of massive galaxies since z~3, we find
that quiescent galaxies lie on the mass FP out to z~2. In contrast with ~1.4
dex evolution in the luminosity FP, average residuals from the z~0 mass FP are
less than ~0.15 dex since z~2. Assuming the Hyde & Bernardi (2009) mass FP
slope, we find that this minimal offset scales as (1+z)^{-0.095+/-0.043}. This
result lends credence to previous studies that derived luminosity evolution
from the FP. Therefore, despite their compact sizes and suggestions that
massive galaxies are more disk-like at z~2, the relationship between their
dynamics and structural properties are consistent with local early-type
galaxies. Finally, we find no strong evidence for a tilt of the mass FP
relative to the Virial plane, but emphasize the need for full models including
selection biases to fully investigate this issue.
