Mapping the hot gas temperature in galaxy clusters using X-ray and Sunyaev-Zel’dovich imaging

¹ Laboratoire Lagrange, Université Côte d’Azur, Observatoire de la Côte d’Azur, CNRS, Blvd de l’Observatoire, CS 34229, 06304 Nice Cedex 4, France
e-mail: remi.adam@oca.eu
² Laboratoire de Physique Subatomique et de Cosmologie, Université Grenoble Alpes, CNRS/IN2P3, 53 avenue des Martyrs, 38400 Grenoble, France
³ Laboratoire AIM, IRFU/Département d’Astrophysique – CEA/DRF – CNRS – Université Paris Diderot, Bât. 709, CEA-Saclay, 91191 Gif-sur-Yvette Cedex, France
⁴ Astronomy Instrumentation Group, University of Cardiff, Cardiff CF10 3XQ, UK
⁵ Institut d’Astrophysique Spatiale (IAS), CNRS and Université Paris Sud, 91400 Orsay, France
⁶ Institut Néel, CNRS and Université Grenoble Alpes, 38400 Grenoble, France
⁷ Institut de RadioAstronomie Millimétrique (IRAM), 18012 Granada, Spain
⁸ Dipartimento di Fisica, Università degli Studi di Roma Tor Vergata, via della Ricerca Scientifica, 1, 00133 Roma, Italy
⁹ Institut de RadioAstronomie Millimétrique (IRAM), 38406 Grenoble, France
¹⁰ Dipartimento di Fisica, Sapienza Università di Roma, Piazzale Aldo Moro 5, 00185 Roma, Italy
¹¹ Institut de Planétologie et d’Astrophysique de Grenoble (IPAG), CNRS and Université Grenoble Alpes, 38406 Saint-Martin-d’Hères France
¹² Aix-Marseille Université, CNRS, LAM (Laboratoire d’Astrophysique de Marseille) UMR 7326, 13388 Marseille, France
¹³ School of Earth and Space Exploration and Department of Physics, Arizona State University, Tempe, AZ 85287, USA
¹⁴ Université de Toulouse, UPS-OMP, Institut de Recherche en Astrophysique et Planétologie (IRAP), 31400 Toulouse, France
¹⁵ CNRS, IRAP, 9 avenue Colonel Roche, BP 44346, 31028 Toulouse Cedex 4, France

Received: 29 September 2016
Accepted: 5 July 2017

Abstract

We propose a method to map the temperature distribution of the hot gas in galaxy clusters that uses resolved images of the thermal Sunyaev-Zel’dovich (tSZ) effect in combination with X-ray data. Application to images from the New IRAM KIDs Array (NIKA) and XMM-Newton allows us to measure and determine the spatial distribution of the gas temperature in the merging cluster MACS J0717.5+3745, at z = 0.55. Despite the complexity of the target object, we find a good morphological agreement between the temperature maps derived from X-ray spectroscopy only – using XMM-Newton (T_XMM) and Chandra (T_CXO) – and the new gas-mass-weighted tSZ+X-ray imaging method (T_SZX). We correlate the temperatures from tSZ+X-ray imaging and those from X-ray spectroscopy alone and find that T_SZX is higher than T_XMM and lower than T_CXO by ~ 10% in both cases. Our results are limited by uncertainties in the geometry of the cluster gas, contamination from kinetic SZ (~10%), and the absolute calibration of the tSZ map (7%). Investigation using a larger sample of clusters would help minimise these effects.