Astronomy and Astrophysics – Astrophysics
Scientific paper
2006-06-05
Mon.Not.Roy.Astron.Soc.371:1755-1759,2006
Astronomy and Astrophysics
Astrophysics
5 pages, 5 figures
Scientific paper
10.1111/j.1365-2966.2006.10815.x
We study the reionization history of the Universe in cosmological models with non-Gaussian density fluctuations, taking them to have a renormalized $\chi^2$ probability distribution function parametrized by the number of degrees of freedom, $\nu$. We compute the ionization history using a simple semi-analytical model, considering various possibilities for the astrophysics of reionization. In all our models we require that reionization is completed prior to $z=6$, as required by the measurement of the Gunn--Peterson optical depth from the spectra of high-redshift quasars. We confirm previous results demonstrating that such a non-Gaussian distribution leads to a slower reionization as compared to the Gaussian case. We further show that the recent WMAP three-year measurement of the optical depth due to electron scattering, $\tau=0.09 \pm 0.03$, weakly constrains the allowed deviations from Gaussianity on the small scales relevant to reionization if a constant spectral index is assumed. We also confirm the need for a significant suppression of star formation in mini-halos, which increases dramatically as we decrease $\nu$.
Avelino Pedro P.
Liddle Andrew R.
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