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J.M. Shull, M. Giroux, J. Tumlinson (Colorado), J. Kriss (STScI), L. Cowie, A. Songaila (Hawaii), W. Zheng, H.W. Moos, W. Oegerle, A. Davidsen, S. Friedman, J. Kruk (JHU), J. Hutchings, D. Morton (NRC/HIA), R. Green (NOAO), E. Jenkins (Princeton), J.-M. Deharveng (MarsLab)
We use the FUSE far-ultraviolet (912-1187 Å) spectrum of the z=2.885 QSO HE2347-4342 (Kriss et al. 2000, AAS abstract) to obtain information about the He II opacity of the intergalactic medium (IGM) and its fluctuations over the redshift interval z = 2.1 - 2.8. The dataset comes from approximately 400 ks of exposure obtained during orbital night, and the spectrum has been binned to optimize the signal-to-noise ratio. We compare the transmitted flux to models of cosmological radiative transfer in the He~II Ly-alpha forest (Fardal, Giroux, & Shull 1998, AJ, 115, 2206). We explore implications for the ionization state of the IGM and the expected opacity fluctuations arising from discrete sources of the metagalactic ionizing flux.
Financial support for this work came from NASA/FUSE contract NAS5-32985. The Colorado group was also supported by NASA Theory grant NAG5-7262.