Sunyaev-Zel’dovich effect at supercluster scales with Planck

A significant fraction of the baryons in the low redshift Universe is expected to be in a warm-hot phase (WHIM) with temperatures of the order of 105-107 K, and with moderate overdensities δ ∼ 10-100 (Cen & Ostriker 1999). This WHIM would be associated to a network of filaments connecting the regions where clusters of galaxies are located. In this work, we have explored the possibility of detecting this WHIM phase with PLANCK, by means of the Sunyaev-Zel'dovich effect (SZE) associated to regions containing superclusters. We have used hydrodynamic simulations including the gas physics, to identify those regions which are similar to present-day superclusters. Six maps of the Comptonization parameter (y) at PLANCK resolution have been prepared from these regions centered in a supercluster. For their analysis, we have excluded those regions in the maps which are associated to identified clusters in the simulation, studying only the SZ signal produced by the remaining gas in the supercluster. We find that the most intense features in these proccesed maps are produced by small haloes (clumps in the simulations which are not identified as clusters), although these clumps are part of filaments. PLANCK should be able to detect at least one intense feature (y > 8 × 10-6) not associated to a cluster for every 8 superclusters. The probability of observing those features is a strong function of the elongation of the supercluster along the line of sight, so detections are most probable in highly elongated superclusters. © Copyright owned by the author(s) under the terms of the Creative Commons Attribution-NonCommercial-ShareAlike Licence.