Probing Galaxies through Quasar Absorption Lines
Contributed Papers | |
Progress in studies of intergalactic He II absorption
Wei Zheng a1, S. F. Anderson a2, G. A. Kriss a3, K. Chiu a1, D. Haggard a2, D. P. Schneider a4, C. J. Hogan a2, D. G. York a5, S. Burles a6 and A. Meiksin a7
a1 Department of Physics and Astronomy, Johns Hopkins University, Baltimore, MD 21218, USA email: zheng@pha.jhu.edu
a2 Department of Astronomy, University of Washington, Seattle, WA 98195, USA
a3 Space Telescope Science Institute, Baltimore, MD 21218, USA
a4 Department of Astronomy and Astrophysics, Pennsylvania State University, University Park, PA 16802, USA
a5 Department of Astronomy, University of Chicago, Chicago, IL 60637, USA
a6 Department of Physics, Massachusetts Institute of Technology, Cambridge, MA 02139, USA
a7 Institute for Astronomy, University of Edinburgh, Blackford Hill, Edinburgh EH9 3HJ, UK
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AbstractSignificant 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.
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