We present Keck LRIS spectroscopy for a sample of 103 massive ( M > 10 ^ { 10.6 } M _ { \odot } ) galaxies with redshifts 0.9 < z < 1.6 .
Of these , 56 are quiescent with high signal-to-noise absorption line spectra , enabling us to determine robust stellar velocity dispersions for the largest sample yet available beyond a redshift of 1 .
Together with effective radii measured from deep Hubble Space Telescope images , we calculate dynamical masses and address key questions relating to the puzzling size growth claimed by many observers for quiescent galaxies over the redshift interval 0 < z < 2 .
Our large sample provides the first opportunity to carefully examine the relationship between stellar and dynamical masses at high redshift .
We find this relation closely follows that determined locally .
We also confirm the utility of the locally-established empirical calibration which enables high-redshift velocity dispersions to be estimated photometrically , and we determine its accuracy to be 35 % .
To address recent suggestions that progenitor bias — the continued arrival of recently-quenched larger galaxies — can largely explain the size evolution of quiescent galaxies , we examine the growth at fixed velocity dispersion assuming this quantity is largely unaffected by the merger history .
Using the velocity dispersion - age relation observed in the local universe , we demonstrate that significant size and mass growth have clearly occurred in individual systems .
Parameterizing the relation between mass and size growth over 0 < z < 1.6 as R \propto M ^ { \alpha } , we find \alpha = 1.6 \pm 0.3 , in agreement with theoretical expectations from simulations of minor mergers .
Relaxing the assumption that the velocity dispersion is unchanging , we examine growth assuming a constant ranking in galaxy velocity dispersion .
This approach is applicable only to the large-dispersion tail of the distribution , but yields a consistent growth rate of \alpha = 1.4 \pm 0.2 .
Both methods confirm that progenitor bias alone is insufficient to explain our new observations and that quiescent galaxies have grown in both size and stellar mass over 0 < z < 1.6 .