Power spectrum of the Sunyaev-Zel’dovich effect

Abstract

The hot gas in the IGM produces anisotropies in the cosmic microwave background (CMB) through the thermal Sunyaev-Zel'dovich (SZ) effect. The SZ effect is a powerful probe of large-scale structure in the universe, and must be carefully subtracted from measurements of the primary CMB anisotropies. We use moving-mesh hydrodynamical simulations to study the 3-dimensional statistics of the gas, and compute the mean Comptonization parameter y and the angular power spectrum of the SZ fluctuations, for different cosmologies. We compare these results with predictions using the Press-Schechter formalism. We find that the two methods agree approximately, but differ in details. We discuss this discrepancy, and show that resolution limits the reliability of our results to the $200\ensuremath{\lesssim}l\ensuremath{\lesssim}2000$ range. For cluster normalized CDM models, we find a mean y-parameter of the order of ${10}^{\ensuremath{-}6},$ one order of magnitude below the current observational limits from the COBE-FIRAS instrument. For these models, the SZ power spectrum is comparable to the primordial power spectrum around $l=2000.$ It is well below the projected noise for the upcoming MAP satellite, and should thus not be a limitation for this mission. It should be easily detectable with the future Planck Surveyor mission. We show that groups and filaments (kT\ensuremath{\lesssim}5 keV) contribute about 50% of the SZ power spectrum at $l=500.$ About half of the SZ power spectrum on these scales are produced at redshifts $z\ensuremath{\lesssim}0.1,$ and can thus be detected and removed using existing catalogs of galaxies and x-ray clusters.