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Morphological Evolution of Distant Galaxies from Adaptive Optics Imaging
We report here on a sample of resolved, infrared images of galaxies atz~0.5 taken with the 10 m Keck Telescope's adaptive optics system. Weregularly achieve a spatial resolution of 0.05" and are thus able toresolve both the disk and bulge components. We have extractedmorphological information for 10 galaxies and compared their propertiesto those of a local sample. The selection effects of both samples wereexplicitly taken into account in order to derive the unbiased resultthat disks at z~0.5 are ~0.6 mag arcsec-2 brighter than, andabout the same size as, local disks. The case with no luminosityevolution is ruled out at 90% confidence. We also find, in a morequalitative analysis, that the bulges of these galaxies have undergone asmaller amount of surface brightness evolution and have also not changedsignificantly in size from z~0.5 to today. This is the first time thistype of morphological evolution has been measured in the infrared and itpoints to the unique power of AO in exploring galaxy evolution.
| Exploring the Structure of Distant Galaxies with Adaptive Optics on the Keck II Telescope
We report on the first observation of cosmologically distant fieldgalaxies with a high-order adaptive optics (AO) system on an 8-10 mclass telescope. Two galaxies were observed at 1.6 μm at an angularresolution as high as 50 mas using the AO system on the Keck IItelescope. Radial profiles of both objects are consistent with those oflocal spiral galaxies and are decomposed into a classic exponential diskand a central bulge. A star-forming cluster or companion galaxy as wellas a compact core are detected in one of the galaxies at a redshift of0.37+/-0.05. We discuss possible explanations for the core including asmall bulge, a nuclear starburst, or an active nucleus. The same galaxyshows a peak disk surface brightness that is brighter than local disksof comparable size. These observations demonstrate the power of AO toreveal details of the morphology of distant faint galaxies and toexplore galaxy evolution.
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