NIKA2: a mm camera for cluster cosmology

TL;DR

NIKA2 is a high-resolution, wide-field millimeter camera designed for detailed Sunyaev-Zeldovich observations of galaxy clusters at high redshifts, aiming to improve cosmological measurements and understand cluster physics.

Contribution

This paper introduces NIKA2, a new mm camera with wide field of view and high resolution, optimized for high-redshift cluster observations, and reports on its pilot studies with the NIKA instrument.

Findings

NIKA2 has a 6.5 arcmin field of view and high angular resolution at 150 and 260 GHz.

Pilot observations with NIKA demonstrate its capability for detailed SZ studies of galaxy clusters.

NIKA2 will enable mapping of 50 clusters at redshifts 0.5 to 0.9.

Abstract

Galaxy clusters constitute a major cosmological probe. However, Planck 2015 results have shown a weak tension between CMB-derived and cluster-derived cosmological parameters. This tension might be due to poor knowledge of the cluster mass and observable relationship. As for now, arcmin resolution Sunyaev-Zeldovich (SZ) observations ({\it e.g.} SPT, ACT and Planck) only allowed detailed studies of the intra cluster medium for low redshift clusters ($z<0.2$). For high redshift clusters ($z>0.5$) high resolution and high sensitivity SZ observations are needed. With both a wide field of view (6.5 arcmin) and a high angular resolution (17.7 and 11.2 arcsec at 150 and 260 GHz), the NIKA2 camera installed at the IRAM 30-m telescope (Pico Veleta, Spain) is particularly well adapted for these observations. The NIKA2 SZ observation program will map a large sample of clusters (50) at redshifts between 0.5 and 0.9. As a pilot study for NIKA2, several clusters of galaxies have been observed with the pathfinder, NIKA, at the IRAM 30-m telescope to cover the various configurations and observation conditions expected for NIKA2.}