We measure and analyse the sizes of 82 massive ( M \geq 10 ^ { 11 } M _ { \odot } ) galaxies at 1.7 \leq z \leq 3 utilizing deep HST NICMOS data taken in the GOODS North and South fields .
Our sample provides the first statistical study of massive galaxy sizes at z > 2 .
We split our sample into disk–like ( Sérsic index n \leq 2 ) and spheroid–like ( Sérsic index n > 2 ) galaxies , and find that at a given stellar mass , disk–like galaxies at z \sim 2.3 are a factor of 2.6 \pm 0.3 smaller than present day equal mass systems , and spheroid–like galaxies at the same redshift are 4.3 \pm 0.7 times smaller than comparatively massive elliptical galaxies today .
We furthermore show that the stellar mass densities of very massive galaxies at z \sim 2.5 are similar to present–day globular clusters with values \sim 2 \times 10 ^ { 10 } M _ { \odot } kpc ^ { -3 }