Resolving the Structure of Ionized Helium in the Intergalactic Medium with the Far Ultraviolet Spectroscopic Explorer-Reference-Cited by-同舟云学术

Resolving the Structure of Ionized Helium in the Intergalactic Medium with the Far Ultraviolet Spectroscopic Explorer

Published:2001-08-10 Issue:5532 Volume:293 Page:1112-1116
ISSN:0036-8075
Container-title:Science
language:en
Short-container-title:Science

Author:

Kriss G. A.¹²,Shull J. M.³,Oegerle W.⁴,Zheng W.²,Davidsen A. F.²,Songaila A.⁵,Tumlinson J.³,Cowie L. L.⁵,Deharveng J.-M.⁶,Friedman S. D.²,Giroux M. L.³,Green R. F.⁷,Hutchings J. B.⁸,Jenkins E. B.⁹,Kruk J. W.²,Moos H. W.²,Morton D. C.⁸,Sembach K. R.²,Tripp T. M.⁹

Affiliation:

1. Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218, USA.

2. Center for Astrophysical Sciences, Department of Physics and Astronomy, Johns Hopkins University, Baltimore, MD 21218, USA.

3. CASA and JILA, Department of Astrophysical and Planetary Sciences, University of Colorado, Campus Box 389, Boulder, CO 80309, USA.

4. Laboratory for Astronomy and Solar Physics, Code 681, NASA/Goddard Space Flight Center, Greenbelt, MD 20771, USA.

5. Institute for Astronomy, University of Hawaii, 2680 Woodlawn Road, Honolulu, HI 96822, USA.

6. Laboratorie d'Astronomie Spatiale, BP 8, 13376 Marseille Cedex 12, France.

7. Kitt Peak National Observatory, National Optical Astronomy Observatories, Post Office Box 26732, 950 North Cherry Avenue, Tucson, AZ 85726, USA.

8. Herzberg Institute of Astrophysics, National Research Council of Canada, Victoria, BC V8X 4M6, Canada.

9. Princeton University Observatory, Princeton, NJ 08544, USA.

Abstract

The neutral hydrogen (H i ) and ionized helium (He ii ) 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 to 1187 angstrom band at a resolving power of 15,000. We resolve the He ii Lyman α (Lyα) 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 N H i > 10 12.3 per square centimeter that account for most of the observed opacity in He ii Lyα. 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 Lyα 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.

Publisher

American Association for the Advancement of Science (AAAS)

Subject

Multidisciplinary

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