Exploring the Structure of Distant Galaxies with Adaptive Optics on the Keck II Telescope

We report on the first observation of cosmologically distant field galaxies with a high‐order adaptive optics (AO) system on an 8–10 m class telescope. Two galaxies were observed at 1.6 μm at an angular resolution as high as 50 mas using the AO system on the Keck II telescope. Radial profiles of both objects are consistent with those of local spiral galaxies and are decomposed into a classic exponential disk and a central bulge. A star‐forming cluster or companion galaxy as well as a compact core are detected in one of the galaxies at a redshift of 0.37 ± 0.05. We discuss possible explanations for the core including a small bulge, a nuclear starburst, or an active nucleus. The same galaxy shows a peak disk surface brightness that is brighter than local disks of comparable size. These observations demonstrate the power of AO to reveal details of the morphology of distant faint galaxies and to explore galaxy evolution.