The imprints of local superclusters on the Sunyaev-Zel'dovich signals and their detectability with Planck

Abstract

We use high-resolution hydrodynamical simulations of large-scale structure formation to study the imprints of the local superclusters on to the full-sky Sunyaev–Zel'dovich (SZ) signals. Following Mathis et al., the initial conditions have been statistically constrained to reproduce the density field within a sphere of 110 Mpc around the Milky Way, as observed in the IRAS 1.2-Jy all-sky redshift survey. As a result, the positions and masses of prominent galaxy clusters and superclusters in our simulations coincide closely with their real counterparts in the local Universe. We present the results of two different runs: one with adiabatic gas physics only, and one also including cooling, star formation and feedback. By analysing the full-sky maps for the thermal and kinetic SZ signals extracted from these simulations, we find that for multipoles with l < 100 the power spectrum is dominated by the prominent local superclusters, and its amplitude at these scales is a factor of 2 higher than that obtained from unconstrained simulations; at lower multipoles (l < 20) this factor can even reach one order of magnitude. We check the influence of the SZ effect from local superclusters on the cosmic microwave background (CMB) power spectrum at small multipoles and find it negligible and with no signs of quadrupole–octopole alignment. However, performing simulations of the CMB radiation including the experimental noise at the frequencies which will be observed by the Planck satellite, we find results suggesting that an estimate of the SZ power spectrum at large scales can be extracted.