The Fundamental Plane ( FP ) of early-type galaxies , relating the effective radius , velocity dispersion , and surface brightness , has long been recognized as a unique tool for analyzing galaxy structure and evolution .
With the discovery of distant quiescent galaxies and the introduction of high sensitivity near-infrared spectrographs , it is now possible to explore the FP out to z \sim 2 .
In this Letter we study the evolution of the FP out to z \sim 2 using kinematic measurements of massive quiescent galaxies ( M _ { * } > 10 ^ { 11 } M _ { \odot } ) .
We find preliminary evidence for the existence of an FP out to z \sim 2 .
The scatter of the FP , however , increases from z \sim 0 to z \sim 2 , even when taking into account the larger measurement uncertainties at higher redshifts .
We find a strong evolution of the zero point from z \sim 2 to z \sim 0 : \Delta \log _ { 10 } M / L _ { g } \propto ( -0.49 \pm 0.03 ) ~ { } z .
In order to assess whether our spectroscopic sample is representative of the early-type galaxy population at all redshifts , we compare their rest-frame g - z colors with those from a larger mass complete sample of quiescent galaxies .
At z > 1 we find that the spectroscopic sample is bluer .
We use the color offsets to estimate a mass-to-light ratio ( M / L ) correction .
The implied FP zero point evolution after correction is significantly smaller : \Delta \log _ { 10 } M / L _ { g } \propto ( -0.39 \pm 0.02 ) ~ { } z .
This is consistent with an apparent formation redshift of z _ { form } = 6.62 ^ { +3.19 } _ { -1.44 } for the underlying population , ignoring the effects of progenitor bias .
A more complete spectroscopic sample is required at z \sim 2 to properly measure the M / L evolution from the FP evolution .