---
_id: '17736'
abstract:
- lang: eng
  text: 'We discuss currently available observational constraints on the reionization
    history of the intergalactic medium (IGM), and the extent to which accreting black
    holes (BHs) and stars can help account for these observations. We argue, based
    on the combined statistics of Lyman α and β absorption in quasar spectra, that
    the IGM contains a significant amount of neutral hydrogen with nH I/nH ≳ 0.1.
    On the other hand, we argue, based on the lack of a strong evolution in the observed
    abundance of Lyman α emitting galaxies beyond z ∼ 5.5, that the mean neutral hydrogen
    fraction cannot exceed nH I/nH ≈ 0.3 at the same redshift. We conclude that the
    IGM is experiencing rapid ionization at redshift z ∼ 6. We find that quasar BHs,
    including faint ones that are individually below the detection thresholds of existing
    optical and X-ray surveys, are unlikely to drive the evolution of the neutral
    fraction around this epoch, because they would over-produce the present-day soft
    X-ray background. On the other hand, the seeds of the z ∼ 6 quasar BHs likely
    appeared at much earlier epochs (z ∼ 20), and produced hard ionizing radiation
    by accretion. These early BHs are promising candidates to account for the high
    redshift (z ∼ 15) ionization implied by the recent cosmic microwave anisotropy
    data from WMAP. Using a model for the growth of BHs by accretion and mergers in
    a hierarchical cosmology, we suggest that the early growth of quasars must include
    a super-Eddington growth phase, and that, although not yet optically identified,
    the FIRST radio survey may have already detected several thousand > 10^8 M⊙ BHs
    at z > 6. '
article_processing_charge: No
author:
- first_name: Zoltán
  full_name: Haiman, Zoltán
  id: 7c006e8c-cc0d-11ee-8322-cb904ef76f36
  last_name: Haiman
citation:
  ama: 'Haiman Z. Probing the reionization history of the Universe. In: Livio M, Casertano
    S, eds. <i>Planets to Cosmology. Essential Science in the Final Years of the Hubble
    Space Telescope</i>. Vol 18.  Space Telescope Science Institute Symposium Series.
    Baltimore: Cambridge University Press; 2009:157-173. doi:<a href="https://doi.org/10.1017/cbo9780511536328.014">10.1017/cbo9780511536328.014</a>'
  apa: 'Haiman, Z. (2009). Probing the reionization history of the Universe. In M.
    Livio &#38; S. Casertano (Eds.), <i>Planets to Cosmology. Essential Science in
    the Final Years of the Hubble Space Telescope</i> (Vol. 18, pp. 157–173). Baltimore:
    Cambridge University Press. <a href="https://doi.org/10.1017/cbo9780511536328.014">https://doi.org/10.1017/cbo9780511536328.014</a>'
  chicago: 'Haiman, Zoltán. “Probing the Reionization History of the Universe.” In
    <i>Planets to Cosmology. Essential Science in the Final Years of the Hubble Space
    Telescope</i>, edited by Mario Livio and Stefano Casertano, 18:157–73.  Space
    Telescope Science Institute Symposium Series. Baltimore: Cambridge University
    Press, 2009. <a href="https://doi.org/10.1017/cbo9780511536328.014">https://doi.org/10.1017/cbo9780511536328.014</a>.'
  ieee: 'Z. Haiman, “Probing the reionization history of the Universe,” in <i>Planets
    to Cosmology. Essential Science in the Final Years of the Hubble Space Telescope</i>,
    vol. 18, M. Livio and S. Casertano, Eds. Baltimore: Cambridge University Press,
    2009, pp. 157–173.'
  ista: 'Haiman Z. 2009.Probing the reionization history of the Universe. In: Planets
    to Cosmology. Essential Science in the Final Years of the Hubble Space Telescope.
    vol. 18, 157–173.'
  mla: Haiman, Zoltán. “Probing the Reionization History of the Universe.” <i>Planets
    to Cosmology. Essential Science in the Final Years of the Hubble Space Telescope</i>,
    edited by Mario Livio and Stefano Casertano, vol. 18, Cambridge University Press,
    2009, pp. 157–73, doi:<a href="https://doi.org/10.1017/cbo9780511536328.014">10.1017/cbo9780511536328.014</a>.
  short: Z. Haiman, in:, M. Livio, S. Casertano (Eds.), Planets to Cosmology. Essential
    Science in the Final Years of the Hubble Space Telescope, Cambridge University
    Press, Baltimore, 2009, pp. 157–173.
conference:
  end_date: 2004-05-06
  location: Baltimore, MD, United States
  name: Proceedings of the Space Telescope Science Institute Symposium
  start_date: 2004-05-03
date_created: 2024-09-06T09:20:03Z
date_published: 2009-08-17T00:00:00Z
date_updated: 2024-09-30T07:02:44Z
day: '17'
doi: 10.1017/cbo9780511536328.014
editor:
- first_name: Mario
  full_name: Livio, Mario
  last_name: Livio
- first_name: Stefano
  full_name: Casertano, Stefano
  last_name: Casertano
extern: '1'
intvolume: '        18'
language:
- iso: eng
main_file_link:
- url: https://doi.org/10.1017/CBO9780511536328.014
month: '08'
oa_version: None
page: 157-173
place: Baltimore
publication: Planets to Cosmology. Essential Science in the Final Years of the Hubble
  Space Telescope
publication_identifier:
  eisbn:
  - '9780511536328'
  isbn:
  - '9780521847582'
publication_status: published
publisher: Cambridge University Press
quality_controlled: '1'
scopus_import: '1'
series_title: ' Space Telescope Science Institute Symposium Series'
status: public
title: Probing the reionization history of the Universe
type: book_chapter
user_id: 317138e5-6ab7-11ef-aa6d-ffef3953e345
volume: 18
year: '2009'
...