AAS 197, January 2001
Session 3. QSO Absorbers and the IGM
Display, Monday, January 8, 2001, 9:30am-7:00pm, Exhibit Hall

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[3.14] FUSE Observations of He II Absorption in the IGM toward HE2347-4342: Spectral Features

G. Kriss (STScI), W. Zheng, W. Oegerle (JHU), J.M. Shull, M. Giroux (Colorado), L. Cowie, A. Songaila (Hawaii), S. Friedman, A. Davidsen, J. Kruk, H.W. Moos, K. Sembach (JHU), R. Green (NOAO), J. Hutchings, D. Morton (NRC/HIA), E. Jenkins, T. Tripp (Princeton), J.-M. Deharveng (LAS), FUSE Team

We have obtained a far-ultraviolet spectrum of the z=2.885 QSO HE2347-4342 covering the 912--1187 Å\ wavelength range using the Far Ultraviolet Spectroscopic Explorer (FUSE). Our observations comprise ~00 ks of data obtained during orbital night. Binned to a resolution of 0.1 Å, the data have a signal-to-noise ratio of ~5, and they are adequate to resolve individual absorption features and voids in the He II Ly\alpha forest. To establish an unabsorbed continuum level, we obtained simultaneous HST observations at longer ultraviolet wavelengths (1150--3100 Å) using the STIS low-resolution gratings G140L and G230L. Based on a direct comparison of features resolved in both the FUSE spectrum and in a Keck spectrum of the HI Ly\alpha forest, we will discuss the ionization state of the intergalactic medium (IGM). If the IGM is photoionized by AGN and/or hot stars, the He II to H I column density ratio will permit us to assess the spectral shape of the metagalactic ionizing flux and discriminate among various models for its origin.

This work is based on data obtained for the Guaranteed Time Team by the NASA-CNES-CSA FUSE mission operated by the Johns Hopkins University. Financial support to U. S. participants has been provided by NASA contract NAS5-32985.

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