Morphological Evolution of Distant Galaxies from Adaptive Optics Imaging

We report here on a sample of resolved, infrared images of galaxies at z ~ 0.5 taken with the 10 m Keck Telescope's adaptive optics system. We regularly achieve a spatial resolution of 0.″05 and are thus able to resolve both the disk and bulge components. We have extracted morphological information for 10 galaxies and compared their properties to those of a local sample. The selection effects of both samples were explicitly taken into account in order to derive the unbiased result that disks at z ~ 0.5 are ~0.6 mag arcsec-2 brighter than, and about the same size as, local disks. The case with no luminosity evolution is ruled out at 90% confidence. We also find, in a more qualitative analysis, that the bulges of these galaxies have undergone a smaller amount of surface brightness evolution and have also not changed significantly in size from z ~ 0.5 to today. This is the first time this type of morphological evolution has been measured in the infrared and it points to the unique power of AO in exploring galaxy evolution.