Searching for the sources responsible for cosmic reionization: Probing the redshift range 7 < z <10 and beyond

Daniel P. Stark, Richard S. Ellis

Research output: Contribution to journalReview articlepeer-review

12 Scopus citations


We review recent observations that suggest that the global star formation rate density of UV-bright galaxies is declining monotonically with redshift over 3 < z < 7 and illustrate the challenges that a continuation of this decline poses in explaining the assembled stellar mass in several z ∼ 6 galaxies deduced from recent Spitzer data. A plausible conclusion is a vigorous period of yet earlier star formation. Prior to JWST and TMT, strong lensing offers a unique probe of the extent of this earlier activity. We discuss the first results of a blind spectroscopic survey of 10 lensing clusters for 8.5 < z < 10 Ly α emitters using NIRSPEC on Keck. We demonstrate this survey is achieving an (unlensed) sensitivity equivalent to a star formation rate of 0.1 M yr-1. A companion survey, now beginning with HST and Spitzer, will target lensed z and J-band drop-outs and probe a ≃ 1 arcmin2 region 1 magnitude deeper than the UDF/NICMOS observations. In combination, both surveys will provide the first constraints on the contribution of early, low luminosity, sources to cosmic reionization.

Original languageEnglish (US)
Pages (from-to)46-52
Number of pages7
JournalNew Astronomy Reviews
Issue number1-3 SPEC. ISS.
StatePublished - Mar 2006


  • Cosmology: observations
  • Galaxies: high redshift
  • Gravitational lensing

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science


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