Detecting the rise and fall of the first stars by their impact on cosmic reionization

Ahn, Kyungjin, Iliev, Ilian T, Shapiro, Paul R, Mellema, Garrelt, Koda, Jun and Mao, Yi (2012) Detecting the rise and fall of the first stars by their impact on cosmic reionization. Astrophysical Journal Letters, 756 (1). L16. ISSN 2041-8205

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The intergalactic medium was reionized before redshift z ∼ 6, most likely by starlight which escaped from early galaxies. The very first stars formed when hydrogen molecules (H2) cooled gas inside the smallest galaxies, minihalos of mass between 105 and 108 solar masses, before redshift z ∼ 40. Minihalo stars then started reionization but could not finish it before the rising background of H2-dissociating soft-ultraviolet starlight choked them off. We confirm this hypothesis by the first large-scale radiative transfer simulations to include minihalo sources and their suppression. We show that reionization began much earlier with minihalo sources than without, and was greatly extended, which boosts the intergalactic electron-scattering optical depth and the large-angle polarization fluctuations of the cosmic microwave background significantly. Although within current WMAP uncertainties, this boost should be readily detectable by Planck. If reionization ended as late as z ov 7, as suggested by other observations, Planck will thereby see the signature of the first stars at high redshift, currently undetectable by any other probe. We also show that minimal reionization models satisfying both the late reionization condition, zov . 7, and the large optical depth condition, τes & 0.085, can be distinguished from our fiducial model under the same constraints by Planck at high confidence level.

Item Type: Article
Keywords: cosmology: theory, galaxies: high-redshift, radiative transfer
Schools and Departments: School of Mathematical and Physical Sciences > Physics and Astronomy
Subjects: Q Science
Q Science > QB Astronomy
Depositing User: Ilian Iliev
Date Deposited: 10 Jun 2013 10:58
Last Modified: 02 Jul 2019 20:23

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