CATS: Optical to Near-Infrared Colors of the Bulge and Disk of Two z=0.7 Galaxies Using HST and Keck Laser Adaptive Optics Imaging

TL;DR

This study uses laser guide star adaptive optics on Keck II to obtain high-resolution near-infrared images of galaxies at z=0.7, enhancing the analysis of their bulge and disk colors in conjunction with HST data.

Contribution

It demonstrates the effectiveness of combining laser guide star AO with HST imaging to study galaxy structures at intermediate redshifts.

Findings

AO images at 2.2 microns are comparable in depth to HST images.

AO images have superior resolution and Strehl ratios compared to NICMOS.

Adding LGS AO improves the quality of galaxy imaging for color analysis.

Abstract

We have employed laser guide star (LGS) adaptive optics (AO) on the Keck II telescope to obtain near-infrared (NIR) images in the Extended Groth Strip (EGS) deep galaxy survey field. This is a continuation of our Center for Adaptive Optics Treasury Survey (CATS) program of targeting 0.5<z<1 galaxies where existing images with the Hubble Space Telescope (HST) are already in hand. Our AO field has already been imaged by the Advanced Camera for Surveys (ACS) and the Near Infared Camera and Multiobject Spectrograph (NICMOS). Our AO images at 2.2 microns (K') are comparable in depth to those from HST, have Strehl ratios up to 0.4, and FWHM resolutions superior to that from NICMOS. By sampling the field with the LGS at different positions, we obtain better quality AO images than with an immovable natural guide star. As examples of the power of adding LGS AO to HST data we study the optical to NIR colors and color gradients of the bulge and disk of two galaxies in the field with z=0.7.