BISPECTRUM OF THE SUNYAEV–ZEL'DOVICH EFFECT

We perform a detailed study of the bispectrum of the Sunyaev–Zel'dovich (SZ) 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 σ8. We find that the bispectrum amplitude scales as BtSZ∝σ11–128, compared to that of the power spectrum, which scales as AtSZ∝σ7–98. 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 cosmic microwave background (CMB) experiments should be able to detect the SZ bispectrum amplitude with high significance, in part due to the low contamination from extragalactic 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.