We use Hubble Space Telescope imaging to study the structural properties of ten of the most massive ( M \geq 10 ^ { 11.25 } ~ { } M _ { \odot } ) quiescent galaxies ( QGs ) in the UKIDSS UDS at 2.5 < z < 3.0 .
The low spatial density of these galaxies required targeted WFC3 H _ { 160 } imaging , as such systems are rare in existing surveys like CANDELS .
We fit Sersic models to the 2D light profiles and find that the median half-light radius is R _ { e } \sim 3 kpc , a factor of \sim 3 smaller than QGs with similar masses at z \sim 0 .
Complementing our sample with similarly massive QGs at lower redshifts , we find that the median size evolves as R _ { e } \propto H ( z ) ^ { -0.85 \pm 0.12 } ( or alternatively , R _ { e } \propto ( 1 + z ) ^ { -0.90 \pm 0.12 } ) .
This rate of evolution is slower than that for lower mass QGs .
When compared to low redshift QGs , the axis ratio distribution for our high redshift massive QG sample is most consistent with those in which spheroids are dominant .
These observations point to earlier size growth among massive QGs that also resulted in spheroidal systems .
Finally , we measured residual-corrected surface brightness profiles for our sample .
These show that the Sersic parameterization is generally representative out to several effective radii and does not miss excess low surface brightness light .
The sizes inferred from the light profiles therefore confirm the compactness of these most massive high redshift QGs .