Deconstructing the kinetic SZ Power Spectrum

TL;DR

This paper develops a new model for the kinetic SZ power spectrum, calibrated with hydrodynamic simulations, to understand astrophysical impacts and improve constraints on reionization history.

Contribution

The authors introduce a novel, simulation-calibrated model of the kSZ power spectrum that accounts for all relevant modes and reduces astrophysical uncertainties.

Findings

Radiative cooling and star formation can decrease the kSZ amplitude by up to 33%.

Variations in helium reionization redshift affect the kSZ amplitude similarly.

Current cosmological constraints introduce about a 15% uncertainty in the kSZ signal.

Abstract

We present a detailed investigation of the impact of astrophysical processes on the shape and amplitude of the kinetic Sunyaev-Zel'dovich (kSZ) power spectrum from the post-reionization epoch. This is achieved by constructing a new model of the kSZ power spectrum which we calibrate to the results of hydrodynamic simulations. By construction, our method accounts for all relevant density and velocity modes and so is unaffected by the limited box size of our simulations. We find that radiative cooling and star-formation can reduce the amplitude of the kSZ power spectrum by up to 33%, or 1 uK^2 at ell = 3000. This is driven by a decrease in the mean gas density in groups and clusters due to the conversion of gas into stars. Variations in the redshifts at which helium reionization occurs can effect the amplitude by a similar fraction, while current constraints on cosmological parameters (namely sigma_8) translate to a further +-15% uncertainty on the kSZ power spectrum. We demonstrate how the models presented in this work can be constrained -- reducing the astrophysical uncertainty on the kSZ signal -- by measuring the redshift dependence of the signal via kSZ tomography. Finally, we discuss how the results of this work can help constrain the duration of reionization via measurements of the kinetic SZ signal sourced by inhomogeneous (or patchy) reionization.