Open AccessThe earliest epoch of re‐ionization in the standard Λ cold dark matter model
Author(s) -
Fukugita M.,
Kawasaki M.
Publication year - 2003
Publication title -
monthly notices of the royal astronomical society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.058
H-Index - 383
eISSN - 1365-2966
pISSN - 0035-8711
DOI - 10.1046/j.1365-8711.2003.06854.x
Subject(s) - physics , cmb cold spot , cosmic microwave background , reionization , astrophysics , cold dark matter , ionization , dark matter , cosmic background radiation , age of the universe , adiabatic process , universe , cosmology , dark ages , epoch (astronomy) , astronomy , anisotropy , dark energy , galaxy , redshift , ion , quantum mechanics
We show that the earliest possible re‐ionization of the Universe is approximately at z ≃ 13.5 and the optical depth is τ≃ 0.17 in the conventionally accepted Λ cold dark matter (ΛCDM) model with adiabatic fluctuations of a flat spectrum normalized to the cosmic microwave background. This is consistent with the re‐ionization found by the Wilkinson Microwave Anisotropy Probe ( WMAP ) (the apparently earlier re‐ionization epoch of the WMAP is ascribed to the adoption of the instantaneous re‐ionization approximation), i.e. the WMAP result is realized only if re‐ionization of the Universe takes place nearly at the maximal efficiency in the ΛCDM model.