Sunyaev-Zel'dovich Predictions for the Planck Surveyor Satellite using the Hubble Volume Simulations

Abstract

We use the billion-particle Hubble Volume simulations to make statistical predictions for the distribution of galaxy clusters that will be observed by the Planck Surveyor satellite through their effect on the cosmic microwave background -- the Sunyaev-Zel'dovich effect. We utilize the lightcone datasets for both critical density (tauCDM) and flat low-density (LambdaCDM) cosmologies: a `full-sky' survey out to $z \sim 0.5$, two `octant' datasets out to beyond $z=1$ and a 100 square degree dataset extending to $z \sim 4$. Making simple, but robust, assumptions regarding both the thermodynamic state of the gas and the detection of objects against an unresolved background, we present the expected number of SZ sources as a function of redshift and angular size, and also by flux (for both the thermal and kinetic effects) for 3 of the relevant HFI frequency channels. We confirm the expectation that Planck will detect around $5\times 10^4$ clusters, though the exact number is sensitive to the choice of several parameters including the baryon fraction, and also to the cluster density profile, so that either cosmology may predict more clusters. We also find that the majority of detected sources should be at $z<1.5$, and we estimate that around one per cent of clusters will be spatially resolved by Planck, though this has a large uncertainty.