IDEAS home Printed from https://ideas.repec.org/a/nat/nature/v427y2004i6977d10.1038_nature02336.html
   My bibliography  Save this article

A large neutral fraction of cosmic hydrogen a billion years after the Big Bang

Author

Listed:
  • J. Stuart B. Wyithe

    (The University of Melbourne)

  • Abraham Loeb

    (Harvard University)

Abstract

The fraction of ionized hydrogen left over from the Big Bang provides evidence for the time of formation of the first stars and quasar black holes in the early Universe; such objects provide the high-energy photons necessary to ionize hydrogen. Spectra of the two most distant known quasars1 show nearly complete absorption of photons with wavelengths shorter than the Lyman α transition of neutral hydrogen, indicating that hydrogen in the intergalactic medium (IGM) had not been completely ionized at a redshift of z ≈ 6.3, about one billion years after the Big Bang. Here we show that the IGM surrounding these quasars had a neutral hydrogen fraction of tens of per cent before the quasar activity started, much higher than the previous lower limits1,2 of ∼0.1 per cent. Our results, when combined with the recent inference of a large cumulative optical depth to electron scattering after cosmological recombination3 therefore suggest the presence of a second peak in the mean ionization history of the Universe.

Suggested Citation

  • J. Stuart B. Wyithe & Abraham Loeb, 2004. "A large neutral fraction of cosmic hydrogen a billion years after the Big Bang," Nature, Nature, vol. 427(6977), pages 815-817, February.
    • Handle: RePEc:nat:nature:v:427:y:2004:i:6977:d:10.1038_nature02336
    DOI: 10.1038/nature02336
    as

    Download full text from publisher

    File URL: https://www.nature.com/articles/nature02336
    File Function: Abstract
    Download Restriction: Access to the full text of the articles in this series is restricted.
    File URL: https://libkey.io/10.1038/nature02336?utm_source=ideas
    LibKey link: if access is restricted and if your library uses this service, LibKey will redirect you to where you can use your library subscription to access this item
    ---><---

    As the access to this document is restricted, you may want to search for a different version of it.

    More about this item

    Statistics

    Access and download statistics

    Corrections

    All material on this site has been provided by the respective publishers and authors. You can help correct errors and omissions. When requesting a correction, please mention this item's handle: RePEc:nat:nature:v:427:y:2004:i:6977:d:10.1038_nature02336. See general information about how to correct material in RePEc.

    If you have authored this item and are not yet registered with RePEc, we encourage you to do it here. This allows to link your profile to this item. It also allows you to accept potential citations to this item that we are uncertain about.

    We have no bibliographic references for this item. You can help adding them by using this form .

    If you know of missing items citing this one, you can help us creating those links by adding the relevant references in the same way as above, for each refering item. If you are a registered author of this item, you may also want to check the "citations" tab in your RePEc Author Service profile, as there may be some citations waiting for confirmation.

    For technical questions regarding this item, or to correct its authors, title, abstract, bibliographic or download information, contact: Sonal Shukla or Springer Nature Abstracting and Indexing (email available below). General contact details of provider: http://www.nature.com .

    Please note that corrections may take a couple of weeks to filter through the various RePEc services.

    IDEAS is a RePEc service. RePEc uses bibliographic data supplied by the respective publishers.