Keck Adaptive Optics Imaging of 0.5 < z < 1 Field Galaxies from the Hubble Space Telescope Archive

Abstract

We have employed natural guide star adaptive optics (AO) on the Keck II telescope to obtain near-infrared (H and K') images of three field galaxies, each of redshift greater than 0.5. These are among the highest-redshift non-active disk galaxies to be imaged with AO. Each of the galaxies was chosen because it had been observed previously with the Hubble Space Telescope (HST) Wide Field Planetary Camera 2 (WFPC2) by others. Our AO images in the near-infrared (NIR) closely match both the depth and high spatial resolution of those optical data. Combining the archival V and I data with our new H and K' images potentially produces a long-wavelength baseline at uniform resolution. The NIR data probe emission well longward of the 4000 Å break at these redshifts and provide stellar fluxes less contaminated by dust. We fitted two-dimensional galaxy bulge+disk models simultaneously in all bands and compare stellar population synthesis modeling to the photometry of these separated components. This is an initial foray into combining HST and AO imaging to produce a high spatial resolution multicolor data set for a large sample of faint galaxies. Our pilot program shows that NIR AO images from large ground-based observatories, augmented by HST images in the optical, can in principle provide a powerful tool for the analysis of faint field galaxies. However, the AO data signal-to-noise ratio will have to be increased, and AO PSFs need to be controlled more carefully than they were here.