Innovations in adaptive optics imaging and spectroscopy: OSIRIS, galaxy surveys, and galaxy mergers

This thesis presents the design, construction, and installation of two instruments designed for use with the Keck Telescopes' Adaptive Optics (AO) Systems. It also presents the results of a near-infrared AO survey to measure the pair fraction in faint field galaxies. The instrumentation portion of the thesis concentrates on two main projects, OSIRIS, a near-infrared integral-field spectrograph, and SHARC, a near-infrared camera. OSIRIS is a facility-class instrument at the Keck Observatory, and offers a relatively new spectroscopic capability of simultaneously acquiring infrared spectra (R ∼ 3900) at up to 3000 contiguous locations in an AO-corrected focal plane. SHARC is a camera developed for the Keck AO Team to use with AO-related engineering tasks, including testing and commissioning of the Next-Generation Wavefront Controller. SHARC images a field of up to 19. ''1 on a side, at a spatial resolution of 0. ''0187 per pixel throughout the near-infrared (1-2.5 mum). Both instruments were developed in the Infrared Laboratory of the UCLA Department of Physics and Astronomy. The remainder of the thesis describes two near-infrared AO galaxy surveys carried out during the construction of OSIRIS using another instrument partially developed by UCLA. The Keck Observatory Near-Infrared AO Camera (NIRC2) was used to image nearly 700 faint field galaxies (mostly at z ∼ 0.5--1.5), with the goal of measuring the near-infrared galaxy pair fraction. This is the first time that AO has been used to measure the pair fraction in field galaxies, and provides a unique opportunity to probe close companions (less than 1'') in the near-infrared. Our measured pair fraction is 0.13 +/- 0.04 in both the H- and K'-bands (1.63mum and 2.12mum) and provides an independent check of optical pair fraction measurements made using the Hubble Space Telescope (HST). While most pairs are observed to have comparable brightness in optical imaging ( deltam < 2 mag), pairs appear to span a much wider range ( deltam < 5--6 mag) in the infrared. Since infrared brightness is more indicative of the actual stellar mass in galaxies, the number of major mergers is probably significantly over-estimated by studies relying solely on optical data.