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Paper: HST/STIS Observations of the He II Gunn-Peterson Effect
Volume: 240, Gas and Galaxy Evolution: A Conference in Honor of the 20th Anniversary of the VLA
Page: 17
Authors: Smette, A.; Heap, S. R.; Williger, G. M.; Tripp, T. M.; Jenkins, E. B.; Songaila, A.
Abstract: We present HST/STIS observations of the He II Gunn-Peterson effect at z~3 towards Q 0302-003 and HE 2347-4342. The observed opacities are significantly larger than the ones predicted by any existing model aimed at reproducing the characteristics of the intergalactic medium. The ratio of He II to HI column densities required to reproduce these opacities indicates that the UV background radiation is softer than the usually assumed Haardt & Madau spectrum, which may be explained by a significant stellar contribution at the HI Lyman limit.
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