Bispectrum of the Sunyaev-Zel'dovich Effect

TL;DR

This paper analyzes the bispectrum of the Sunyaev-Zel'dovich effect, demonstrating its sensitivity to cosmological parameters and its potential for improved measurements with current high-resolution CMB experiments.

Contribution

It introduces an analytical model linking the SZ bispectrum to sigma_8, highlighting its advantages over the power spectrum in cosmological studies.

Findings

SZ bispectrum scales as sigma_8^{11-12}

Primarily sourced by massive clusters at z~0.4

Detectable with high significance by current CMB experiments

Abstract

We perform a detailed study of the bispectrum of the Sunyaev-Zel'dovich effect. Using an analytical model for the pressure profiles of the intracluster medium, we demonstrate the SZ bispectrum to be a sensitive probe of the amplitude of the matter power spectrum parameter sigma_8. We find that the bispectrum amplitude scales as B_SZ ~ sigma_8^{11-12}, compared to that of the power spectrum, which scales as A_tSZ ~ sigma_8^{7-9}. We show that the SZ bispectrum is principally sourced by massive clusters at redshifts around z~0.4, which have been well-studied observationally. This is in contrast to the SZ power spectrum, which receives a significant contribution from less-well understood low-mass and high-redshift groups and clusters. Therefore, the amplitude of the bispectrum at l~3000 is less sensitive to astrophysical uncertainties than the SZ power spectrum. We show that current high resolution CMB experiments should be able to detect the SZ bispectrum amplitude with high significance, in part due to the low contamination from extra-galactic foregrounds. A combination of the SZ bispectrum and the power spectrum can sharpen the measurements of thermal and kinetic SZ components and help distinguish cosmological and astrophysical information from high-resolution CMB maps.