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Resolving the Structure of Ionized Helium in the Intergalactic Medium with the Far Ultraviolet Spectroscopic Explorer | | G. A. Kriss
; J. M. Shull
; W. Oegerle
; W. Zheng
; A. F. Davidsen
; A. Songaila
; J. Tumlinson
; L. L. Cowie
; J.-M. Deharveng
; S. D. Friedman
; M. L. Giroux
; R. F. Green
; J. B. Hutchings
; E. B. Jenkins
; J. W. Kruk
; H. W. Moos
; D. C. Morton
; K. R. Sembach
; T. M. Tripp
; | | Date: |
9 Aug 2001 | | Journal: | Science, 293, 5532 (2001) 1112. http://www.sciencemag.org/cgi/content/full/293/5532/1112 | | Subject: | astro-ph | | Affiliation: | 1,2), J. M. Shull , W. Oegerle , W. Zheng , A. F. Davidsen , A. Songaila , J. Tumlinson , L. L. Cowie , J.-M. Deharveng , S. D. Friedman , M. L. Giroux , R. F. Green , J. B. Hutchings , E. B. Jenkins , J. W. Kruk , H. W. Moos , D. C. Morton , K. R. Se | | Abstract: | The neutral hydrogen and the ionized helium absorption in the spectra of quasars are unique probes of structure in the early universe. We present Far-Ultraviolet Spectroscopic Explorer observations of the line of sight to the quasar HE2347-4342 in the 1000-1187 A band at a resolving power of 15,000. We resolve the He II Ly alpha absorption as a discrete forest of absorption lines in the redshift range 2.3 to 2.7. About 50 percent of these features have H I counterparts with column densities log N(HI) > 12.3 that account for most of the observed opacity in He II Ly alpha. The He II to H I column density ratio ranges from 1 to >1000 with an average of ~80. Ratios of <100 are consistent with photoionization of the absorbing gas by a hard ionizing spectrum resulting from the integrated light of quasars, but ratios of >100 in many locations indicate additional contributions from starburst galaxies or heavily filtered quasar radiation. The presence of He II Ly alpha absorbers with no H I counterparts indicates that structure is present even in low-density regions, consistent with theoretical predictions of structure formation through gravitational instability. | | Source: | arXiv, astro-ph/0108169 | | Other source: | [GID 759882] pmid11498584 | | Services: | Forum | Review | PDF | Favorites | |
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