Abstract
During the epoch of reionization, local variations in the ionized fraction (patchiness) imprint arcminute-scale temperature anisotropies in the cosmic microwave background through the kinetic Sunyaev–Zel’dovich (kSZ) effect. We employ an analytic model of reionization devised by Furlanetto and coworkers to calculate the kSZ anisotropies for patchy reionization. We find that the angular power spectrum of the kSZ anisotropies depends strongly on the size distribution of the HII bubbles and on the duration of reionization. In addition, we show that upcoming measurements of the kSZ effect should be able to distinguish between several popular reionization scenarios. In particular, the amplitude of the patchy power spectrum for reionization scenarios in which the IGM is significantly ionized by Population III stars (or by mini-quasars/decaying particles) can be larger (or smaller) by over a factor of 3 than the amplitude in more traditional reionization histories (with temperature anisotropies that range between 0.5 and 3 μK at l = 5000).
Highlights
Scattering of cosmic microwave background (CMB) photons off objects after recombination imprints hot and cold spots in the CMB
We find that the angular power spectrum of the kinetic Sunyaev-Zel’dovich (kSZ) anisotropies depends strongly on the size distribution of the H in models (I) and (II) bubbles and on the duration of reionization
The amplitude of the patchy power spectrum for reionization scenarios in which the IGM is significantly ionized by Population III stars can be larger by over a factor of 3 than the amplitude in more traditional reionization histories
Summary
Scattering of cosmic microwave background (CMB) photons off objects after recombination imprints hot and cold spots in the CMB Measurement of these secondary anisotropies will elucidate details of the formation and evolution of structure in the universe, including the morphology of reionization. We employ the analytic model outlined in Furlanetto et al (2004b, hereafter FZH04) to calculate the kSZ signal for many different reionization histories. Most analytic models of reionization are based on the growth of H II regions around individual galaxies or quasars (Arons & Wingert 1972; Barkana & Loeb 2001) This contrasts with current state-of-the-art simulations (Sokasian et al 2003, 2004; Ciardi et al 2003; Furlanetto et al 2004d), which find a relatively small number of large ionized regions around clusters of sources.
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