Observational constraints of the end of cosmic reionization

Research output: Chapter in Book/Report/Conference proceedingConference contribution

1 Scopus citations


The epoch of reionization is the last unexplored phase of cosmic evolution, corresponding to a crucial era in cosmic structure formation - the formation of the first luminous objects. I review some recent constraints on the end of reionization using observations of the highest redshift quasars and galaxies. Spectroscopic studies of Gunn-Peterson (GP) absorption, and related phenomena, suggest a qualitative change in the state of the intergalactic medium (IGM) at z∼6, indicating a rapid increase in the neutral fraction of the IGM, from xHI<10-4 at z≤5.5, to xHI>10 -3, and perhaps as high as 0.3, at z≥6. On the other hand, transmission spikes in the GP trough, and observations of the evolution of the Lyα galaxy luminosity function indicate xHI<50% at z∼6.5. The IGM characteristics at this epoch are consistent with the end of the overlapping stage of reionization. Current data are consistent with star forming galaxies, in particular low luminosity galaxies, rather than quasars and AGNs, as being the dominant sources of reionizing photons, although large uncertainties still exist in estimating the total contribution from the galaxy population at high-redshift.

Original languageEnglish (US)
Title of host publicationFirst Stars III
Number of pages5
StatePublished - 2008
EventFirst Stars III - Santa Fe, NM, United States
Duration: Jul 15 2007Jul 20 2007

Publication series

NameAIP Conference Proceedings
ISSN (Print)0094-243X
ISSN (Electronic)1551-7616


OtherFirst Stars III
Country/TerritoryUnited States
CitySanta Fe, NM


  • Galaxy evolution
  • Intergalactic medium
  • Quasars
  • Reionization

ASJC Scopus subject areas

  • Physics and Astronomy(all)


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