Isocurvature fluctuations induce early star formation

Naoshi Sugiyama, Saleem Zaroubi, Joseph Silk

Research output: Contribution to journalArticlepeer-review


The early reionization of the Universe inferred from the WMAP polarization results, if confirmed, poses a problem for the hypothesis that scale-invariant adiabatic density fluctuations account for large-scale structure and galaxy formation. One can only generate the required amount of early star formation if extreme assumptions are made about the efficiency and nature of early reionization. We develop an alternative hypothesis that invokes an additional component of a non-scale-free isocurvature power spectrum together with the scale-free adiabatic power spectrum for inflation-motivated primordial density fluctuations. Such a component is constrained by the Lyman alpha forest observations, can account for the small-scale power required by spectroscopic gravitational lensing, and yields a source of early star formation that can reionize the Universe at z ∼ 20 yet becomes an inefficient source of ionizing photons by z ∼ 10, thereby allowing the conventional adiabatic fluctuation component to reproduce the late thermal history of the intergalactic medium.

Original languageEnglish
Pages (from-to)543-548
Number of pages6
JournalMonthly Notices of the Royal Astronomical Society
Issue number2
StatePublished - 21 Oct 2004
Externally publishedYes


  • Cosmology: theory
  • Early Universe
  • Galaxies: formation-intergalactic medium
  • Large-scale structure of Universe
  • Stars: formation


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