The Impact of Cooling and Heating on the Sunyaev–zel’dovich Effect

We use hydrodynamical simulations to assess the impact of radiative cooling and ‘pre-heating’ on predictions for the Sunyaev–Zel’dovich (SZ) effect. We find that cooling significantly reduces both the mean SZ signal and its angular power spectrum. Pre-heating can give a higher mean distortion, while leaving the angular power spectrum below that found in a simulation without heating or cooling. We look at the relative contribution from high and low density gas to the thermal and kinetic effects, and find that in the cooling model about 60 per cent of the mean thermal distortion arises from low overdensity gas. We find that haloes dominate the thermal SZ power spectrum in all models, while in the cooling simulation the kinetic SZ power spectrum originates predominantly in lower overdensity gas. Subject headings: cosmic microwave background – cosmology: theory – galaxies: clusters: general – large-scale structure of universe – methods: numerical