Gemini K-band NIRI Adaptive Optics Observations of Massive Galaxies at 1
  < z < 2
  We present deep K-band adaptive-optics observations of eight very massive (M*
~ 4 x 10^11 Msun) galaxies at 1 < z < 2 utilizing the Gemini NIRI/Altair Laser
Guide System. These systems are selected from the Palomar Observatory
Wide-Field Infrared (POWIR) survey, and are amongst the most massive field
galaxies at these epochs. The depth and high spatial resolution of our images
allow us to explore for the first time the stellar mass surface density
distribution of massive distant galaxies from 1 to 15 kpc on an individual
galaxy basis, rather than on stacked images. We confirm that some of these
massive objects are extremely compact with measured effective radii between
0."1 - 0."2, giving sizes which are < 2 kpc, a factor of ~ 7 smaller in
effective radii than similar mass galaxies today. Examining stellar mass
surface densities as a function of fixed physical aperture, we find an
over-density of material within the inner profiles, and an under-density in the
outer profile, within these high-z galaxies compared with similar mass galaxies
in the local universe. Consequently, massive galaxies should evolve in a way to
decrease the stellar mass density in their inner region, and at the same time
creating more extensive outer light envelopes. We furthermore show that ~ 38%
+- 20% of our sample contains evidence for a disturbed outer stellar matter
distribution suggesting that these galaxies are undergoing a recent dynamical
episode, such as a merger or accretion event. We calculate that massive
galaxies at z < 2 will undergo on the order of five of these events, a much
higher rate than observed for major mergers, suggesting that these galaxies are
growing in size and stellar mass in part through minor mergers during this
epoch.
