A low-mass galaxy cluster as a test-case study for the NIKA2 SZ Large Program

TL;DR

This study demonstrates the capability of NIKA2 to accurately map the thermal Sunyaev-Zel'dovich effect in faint, low-mass galaxy clusters by effectively modeling point source contamination, aiding cosmological analyses.

Contribution

It introduces a joint fitting method for SZ signal and point source fluxes, improving thermodynamic property estimation in low-SNR galaxy clusters.

Findings

Successful joint fit of SZ signal and point source fluxes.

Effective contamination correction enables thermodynamic analysis.

Promising results for faint, low-mass clusters with high contamination.

Abstract

High-resolution mapping of the hot gas in galaxy clusters is a key tool for cluster-based cosmological analyses. Taking advantage of the NIKA2 millimeter camera operated at the IRAM 30-m telescope, the NIKA2 SZ Large Program seeks to get a high-resolution follow-up of 45 galaxy clusters covering a wide mass range at high redshift in order to re-calibrate some of the tools needed for the cosmological exploitation of SZ surveys. We present the second cluster analysis of this program, targeting one of the faintest sources of the sample in order to tackle the difficulties in data reduction for such faint, low-SNR clusters. In this study, the main challenge is the precise estimation of the contamination by sub-millimetric point sources, which greatly affects the tSZ map of the cluster. We account for this contamination by performing a joint fit of the SZ signal and of the flux density of the compact sources. A prior knowledge of these fluxes is given by the adjustment of the SED of each source using data from both NIKA2 and the \textit{Herschel} satellite. The first results are very promising and demonstrate the possibility to estimate thermodynamic properties with NIKA2, even in a compact cluster heavily contaminated by point sources.