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R. Simcoe, W. Sargent (Caltech), M. Rauch (OCIW)
Recent observations using the FUSE satellite and HST/STIS have emphasized the contribution of shock-heated O VI to the local baryon budget. Also, photoionized O VI is well known to be an excellent tracer of metal enrichment in the lowest density regions of the IGM. Searches for oxygen at higher redshift from the ground have been limited by severe bending of the doublet with lines in the lyman-alpha and lyman-beta forests. However, there exists a growing body of both direct (at high column density) and statistical (at low column density) evidence that suggests the presence of O VI at a wide range of associated H I column densities, even at large lookback times. We will discuss progress on a systematic, large pathlength search for O VI absorption in the spectra of a sample of quasars observed with the Keck I telescope and HIRES spectrograph, and we will describe our strategy for dealing with the blending problem. Where O VI is unambiguously detected, we compare its abundance and kinematics with those of other highly ionized species. We will also discuss the initial results of statistcial searches for oxygen at the weakest levels of absorption.