The Kinetic Sunyaev‐Zel’dovich Effect from Radiative Transfer Simulations of Patchy Reionization

We present the first calculation of the kinetic Sunyaev-Zel'dovich (kSZ)effect due to the inhomogeneous reionization of the universe based on detailedlarge-scale radiative transfer simulations of reionization. The resulting skypower spectra peak at l=2000-8000 with maximum values ofl^2C_l~1\times10^{-12}. The peak scale is determined by the typical size of theionized regions and roughly corresponds to the ionized bubble sizes observed inour simulations, ~5-20 Mpc. The kSZ anisotropy signal from reionizationdominates the primary CMB signal above l=3000. This predicted kSZ signal atarcminute scales is sufficiently strong to be detectable by upcomingexperiments, like the Atacama Cosmology Telescope and South Pole Telescopewhich are expected to have ~1' resolution and ~muK sensitivity. The extendedand patchy nature of the reionization process results in a boost of the peaksignal in power by approximately one order of magnitude compared to a uniformreionization scenario, while roughly tripling the signal compared with thatbased upon the assumption of gradual but spatially uniform reionization. Atlarge scales the patchy kSZ signal depends largely on the ionizing sourceefficiencies and the large-scale velocity fields: sources which produce photonsmore efficiently yield correspondingly higher signals. The introduction ofsub-grid gas clumping in the radiative transfer simulations producessignificantly more power at small scales, and more non-Gaussian features, buthas little effect at large scales. The patchy nature of the reionizationprocess roughly doubles the total observed kSZ signal for l~3000-10^4 comparedto non-patchy scenarios with the same total electron-scattering optical depth.Comment: 14 pages, 13 figures (some in color), submitted to Ap