Cosmology with the pairwise kinematic SZ effect: Calibration and validation using hydrodynamical simulations

TL;DR

This paper evaluates the potential of the pairwise kinematic Sunyaev-Zel'dovich effect as a cosmological probe using hydrodynamical simulations, focusing on calibration, uncertainties, and systematic effects.

Contribution

It introduces a calibration method linking Compton-y and optical depth to accurately estimate pairwise velocities from the kSZ effect.

Findings

A scaling relation between Compton-y and optical depth enables accurate velocity estimates.

The kSZ effect can serve as a significant cosmological probe with proper calibration.

Systematic effects and feedback models impact the interpretation of high-precision measurements.

Abstract

We study the potential of the kinematic SZ effect as a probe for cosmology, focusing on the pairwise method. The main challenge is disentangling the cosmologically interesting mean pairwise velocity from the cluster optical depth and the associated uncertainties on the baryonic physics in clusters. Furthermore, the pairwise kSZ signal might be affected by internal cluster motions or correlations between velocity and optical depth. We investigate these effects using the Magneticum cosmological hydrodynamical simulations, one of the largest simulations of this kind performed to date. We produce tSZ and kSZ maps with an area of $\simeq 1600~\mathrm{deg}^2$, and the corresponding cluster catalogues with $M_{500c} \gtrsim 3 \times 10^{13}~h^{-1}M_\odot$ and $z \lesssim 2$. From these data sets we calibrate a scaling relation between the average Compton-$y$ parameter and optical depth. We show that this relation can be used to recover an accurate estimate of the mean pairwise velocity from the kSZ effect, and that this effect can be used as an important probe of cosmology. We discuss the impact of theoretical and observational systematic effects, and find that further work on feedback models is required to interpret future high-precision measurements of the kSZ effect.