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Progress in studies of intergalactic He II absorption

Published online by Cambridge University Press:  06 October 2005

Wei Zheng ,
S. F. Anderson ,
G. A. Kriss ,
K. Chiu ,
D. Haggard ,
D. P. Schneider ,
C. J. Hogan ,
D. G. York ,
S. Burles  and
A. Meiksin
Wei Zheng
Affiliation:
Department of Physics and Astronomy, Johns Hopkins University, Baltimore, MD 21218, USA email: zheng@pha.jhu.edu
S. F. Anderson
Affiliation:
Department of Astronomy, University of Washington, Seattle, WA 98195, USA
G. A. Kriss
Affiliation:
Space Telescope Science Institute, Baltimore, MD 21218, USA
K. Chiu
Affiliation:
Department of Physics and Astronomy, Johns Hopkins University, Baltimore, MD 21218, USA email: zheng@pha.jhu.edu
D. Haggard
Affiliation:
Department of Astronomy, University of Washington, Seattle, WA 98195, USA
D. P. Schneider
Affiliation:
Department of Astronomy and Astrophysics, Pennsylvania State University, University Park, PA 16802, USA
C. J. Hogan
Affiliation:
Department of Astronomy, University of Washington, Seattle, WA 98195, USA
D. G. York
Affiliation:
Department of Astronomy, University of Chicago, Chicago, IL 60637, USA
S. Burles
Affiliation:
Department of Physics, Massachusetts Institute of Technology, Cambridge, MA 02139, USA
A. Meiksin
Affiliation:
Institute for Astronomy, University of Edinburgh, Blackford Hill, Edinburgh EH9 3HJ, UK
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Abstract

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Significant progress has been made in the last decade toward an understanding of the intergalactic He II absorption. At redshifts $z<2.8$, individual absorbers are found to be ionised mainly by a hard quasar continuum, but their ionisation states vary considerably and the ionising radiation field may have contributions from a soft stellar continuum. The He II opacity increases significantly at $z\sim 2.8$, suggesting a possible end of the general reionisation of intergalactic He II. Using the massive SDSS database and UV selection with HST and GALEX, we have found new quasars at $z>3.5$, with detected He II absorption. Future observations will pinpoint the epoch of reionisation of the intergalactic He II.

Type
Contributed Papers
Information
Proceedings of the International Astronomical Union , Volume 1 , Colloquium C199: Probing Galaxies through Quasar Absorption Lines , March 2005 , pp. 484 - 486
Copyright
© 2005 International Astronomical Union