Precision era of the kinetic Sunyaev–Zel'dovich effect: simulations, analytical models and observations and the power to constrain reionization

The kinetic Sunyaev–Zel'dovich effect, which is the dominant cosmic microwave background (CMB) source at arcmin scales and ν∼ 217 GHz , probes the ionized gas peculiar momentum up to the epoch of reionization and is a sensitive measure of the reionization history. We ran high‐resolution self‐similar and ΛCDM hydro‐simulations and built an analytical model to study this effect. Our model reproduces the ΛCDM simulation results to several per cent accuracy, passes various tests against self‐similar simulations, and shows a wider range of applicability than previous analytical models. Our model in its continuous version is free of simulation limitations, such as a finite simulation box and finite resolution, and allows an accurate prediction of the kinetic SZ power spectrum, C l . For the Wilkinson Microwave Anisotropy Probe cosmology, we find l 2 C l /(2π) ≃ 0.91 × 10 −12 [(1 + z reion )/10] 0.34 (l/5000)   0.23‐0.015( z   reion − 9)for the reionization redshift 6 < z reion < 20 and 3000 < l < 9000 . The corresponding temperature fluctuation is several μK at these ranges. The dependence of C l on the reionization history allows an accurate measurement of the reionization epoch. For the Atacama Cosmology Telescope (ACT) experiment, C l can be measured with ∼1 per cent accuracy. C l scales as (Ω b h ) 2 σ 4∼6 8 . Given cosmological parameters, ACT would be able to constrain z reion with several per cent accuracy. Some multireionization scenarios degenerate in the primary CMB temperature and temperature–E polarization (TE) measurement can be distinguished with ∼ 10 σ confidence.