NIKA2: a millimeter camera for cluster cosmology

Abstract

International audienceGalaxy clusters constitute a major cosmological probe. However, Planck 2015 results have showna weak tension between CMB-derived and cluster-derived cosmological parameters. This tensionmight be due to poor knowledge of the cluster mass and observable relationship. As for now,arcmin resolution Sunyaev-Zeldovich (SZ) observations (e.g. SPT, ACT and Planck) only alloweddetailed studies of the intra cluster medium for low redshift clusters (z 0:5) high resolution and high sensitivity SZ observations are needed. With botha wide field of view (6.5 arcmin) and a high angular resolution (17.7 and 11.2 arcsec at 150and 260 GHz), the NIKA2 camera installed at the IRAM 30-m telescope (Pico Veleta, Spain) isparticularly well adapted for these observations. The NIKA2 SZ observation program will map alarge sample of clusters (50) at redshifts between 0.5 and 0.9. As a pilot study for NIKA2, severalclusters of galaxies have been observed with the pathfinder, NIKA, at the IRAM 30-m telescopeto cover the various configurations and observation conditions expected for NIKA2