EDP Sciences Journals List
Advanced Search
Subscriber Authentication Point
Home All issues Volume 442/1 Article
Free access article

Issue A&A
Volume 442, Number 1, October IV 2005
Page(s) 63 - 68
Section Cosmology (including clusters of galaxies)
DOI http://dx.doi.org/10.1051/0004-6361:20053365



A&A 442, 63-68 (2005)
DOI: 10.1051/0004-6361:20053365

Intergalactic HeII absorption towards QSO 1157+3143

D. Reimers1, C. Fechner1, H.-J. Hagen1, P. Jakobsen2, D. Tytler3 and D. Kirkman3

1  Hamburger Sternwarte, Universität Hamburg, Gojenbergsweg 112, 21029 Hamburg, Germany
    e-mail: cfechner@hs.uni-hamburg.de
2  Astrophysics Missions Division, RSSD, European Space Agency, ESTEC, 2200 AG Noordwijk, The Netherlands
3  Center for Astrophysics and Space Sciences, University of California, San Diego, MS 0424, La Jolla, CA 92093-0424, USA

(Received 4 May 2005/ Accepted 30 June 2005 )

Abstract
We report the discovery of a further line of sight allowing detection of $\ion{He}{ii}$ Ly$\alpha$ absorption by the intergalactic medium. A HST/STIS survey of 32 bright $z \sim 3$ quasars selected from the Hamburg Quasar Surveys yielded one detection toward QSO 1157+3143 ( $z \sim 3, B \simeq 17$). A 10 orbit follow-up spectrum reveals a UV spectrum significantly suppressed by two intervening Lyman limit systems at z=2.77 and 2.94, but with the continuum flux recovering sufficiently shortward of ~ $1700\,{\rm\AA}$ to allow study of the $\ion{He}{ii}$ absorption spectrum in the redshift range $2.75 \leq z \leq 2.97$. The absorption is characterized by alternating voids and dense filament structures seen in both $\ion{He}{ii}$ and $\ion{H}{i}$. Attempts to model the $\ion{He}{ii}$ opacity in terms of $\ion{H}{i}$ Ly$\alpha$ forest absorption are not successful in the voids, suggesting that $\ion{He}{ii}$ reionization is not complete between z=2.77 and 2.97 or that an optically thin Lyman limit system with $z \approx 0.3$ is responsible for the additional opacity.


Key words: galaxies: quasars: individual: QSO 1157+3143 -- galaxies: quasars: absorption lines -- cosmology: observations

SIMBAD Objects



© ESO 2005


What is OpenURL?

The OpenURL standard is a protocol for transmission of metadata describing the resource that you wish to access. An OpenURL link contains article metadata and directs it to the OpenURL server of your choice. The OpenURL server can provide access to the resource and also offer complementary services (specific search engine, export of references...). The OpenURL link can be generated by different means.
  • If your librarian has set up your subscription with an OpenURL resolver, OpenURL links appear automatically on the abstract pages.
  • You can define your own OpenURL resolver with your EDPS Account. In this case your choice will be given priority over that of your library.
  • You can use an add-on for your browser (Firefox or I.E.) to display OpenURL links on a page (see http://www.openly.com/openurlref/). You should disable this module if you wish to use the OpenURL server that you or your library have defined.