Pressure distribution of the high-redshift cluster of galaxies CL J1226.9+3332 with NIKA

TL;DR

This study presents high-resolution tSZ observations of the high-redshift galaxy cluster CL J1226.9+3332, combining NIKA, Planck, and Chandra data to analyze its pressure, mass, and thermal properties, demonstrating the potential of high-res tSZ for distant cluster studies.

Contribution

First high-resolution tSZ imaging of a high-redshift galaxy cluster using NIKA, combined with X-ray and Planck data to derive detailed physical profiles and mass estimates.

Findings

Cluster is morphologically relaxed on large scales

Total mass within R500 is approximately 6 x 10^14 solar masses

High-resolution tSZ effectively probes high-redshift cluster properties

Abstract

The thermal Sunyaev-Zel'dovich (tSZ) effect is expected to provide a low scatter mass proxy for galaxy clusters since it is directly proportional to the cluster thermal energy. The tSZ observations have proven to be a powerful tool for detecting and studying them, but high angular resolution observations are now needed to push their investigation to a higher redshift. In this paper, we report high angular (< 20 arcsec) resolution tSZ observations of the high-redshift cluster CL J1226.9+3332 (z=0.89). It was imaged at 150 and 260 GHz using the NIKA camera at the IRAM 30-meter telescope. The 150 GHz map shows that CL J1226.9+3332 is morphologically relaxed on large scales with evidence of a disturbed core, while the 260 GHz channel is used mostly to identify point source contamination. NIKA data are combined with those of Planck and X-ray from Chandra to infer the cluster's radial pressure, density, temperature, and entropy distributions. The total mass profile of the cluster is derived, and we find $M_{500} = 5.96^{+1.02}_{-0.79} $ x $10^{14} M_{\odot}$ within the radius $R_{500} = 930^{+50}_{-43}$ kpc, at a 68% confidence level. ($R_{500}$ is the radius within which the average density is 500 times the critical density at the cluster's redshift.) NIKA is the prototype camera of NIKA2, a KIDs (kinetic inductance detectors) based instrument to be installed at the end of 2015. This work is, therefore, part of a pilot study aiming at optimizing tSZ NIKA2 large programs.