Using stellar kinematics measurements , we investigate the growth of massive , quiescent galaxies from z \sim 2 to today .
We present X-Shooter spectra from the UV to NIR and dynamical mass measurements of five quiescent massive ( > 10 ^ { 11 } M _ { \odot } ~ { } ) galaxies at z \sim 2 .
This triples the sample of z > 1.5 galaxies with well constrained ( \delta \sigma < 100 km s ^ { -1 } ) velocity dispersion measurements .
From spectral population synthesis modeling we find that these galaxies have stellar ages that range from 0.5-2 Gyr , with no signs of ongoing star formation .
We measure velocity dispersions ( 290-450 km s ^ { -1 } ) from stellar absorption lines and find that they are 1.6-2.1 times higher than those of galaxies in the Sloan Digital Sky Survey at the same mass .
Sizes are measured using GALFIT from Hubble Space Telescope Wide Field Camera 3 H _ { 160 } and UDS K-band images .
The dynamical masses correspond well to the spectral energy distribution based stellar masses , with dynamical masses that are \sim 15 \% higher .
We find that M _ { * } / M _ { { dyn } } may decrease slightly with time , which could reflect the increase of the dark matter fraction within an increasing effective radius .
We combine different stellar kinematic studies from the literature , and examine the structural evolution from z \sim 2 to z \sim 0 : we confirm that at fixed dynamical mass , the effective radius increases by a factor of \sim 2.8 , and the velocity dispersion decreases by a factor of \sim 1.7 .
The mass density within one effective radius decreases by a factor of \sim 20 , while within a fixed physical radius ( 1 kpc ) it decreases only mildly ( factor of \sim 2 ) .
When we allow for an evolving mass limit by selecting a population of galaxies at fixed number density , a stronger size growth with time is found ( factor of \sim 4 ) , velocity dispersion decreases by a factor of \sim 1.4 , and interestingly , the mass density within 1 kpc is consistent with no evolution .
This finding suggests that massive quiescent galaxies at z \sim 2 grow inside-out , consistent with the expectations from minor mergers .