Radio halos in a mass-selected sample of 75 galaxy clusters

I. Sample selection and data analysis^⋆

¹ Hamburger Sternwarte, Universität Hamburg, Gojenbergsweg 112, 21029 Hamburg, Germany
e-mail: vcuciti@hs.uni-hamburg.de
² INAF-Istituto di Radioastronomia, Via P. Gobetti 101, 40129 Bologna, Italy
³ Dipartimento di Fisica e Astronomia, Università di Bologna, Via P. Gobetti 93/2, 40129 Bologna, Italy
⁴ Leiden Observatory, Leiden University, PO Box 9513, 2300 RA Leiden, The Netherlands
⁵ National Centre for Radio Astrophysics, Tata Institute of Fundamental Research Savitribai Phule Pune University Campus, Pune, 411 007 Maharashtra, India
⁶ AIM, CEA, CNRS, Université Paris-Saclay, Université Paris Diderot, Sorbonne Paris Cité, 91191 Gif-sur-Yvette, France
⁷ INAF, Osservatorio di Astrofisica e Scienza dello Spazio, Via Pietro Gobetti 93/3, 40129, Bologna, Italy
⁸ INFN, Sezione di Bologna, Viale Berti Pichat 6/2, 40127 Bologna, Italy
⁹ Naval Research Laboratory, 4555 Overlook Avenue SW, Code 7213, Washington DC 20375, USA

Received: 18 August 2020
Accepted: 26 November 2020

Abstract

Context. Radio halos are synchrotron diffuse sources at the centre of a fraction of galaxy clusters. The study of large samples of clusters with adequate radio and X-ray data is necessary to investigate the origin of radio halos and their connection with the cluster dynamics and formation history.

Aims. The aim of this paper is to compile a well-selected sample of galaxy clusters with deep radio observations to perform an unbiased statistical study of the properties of radio halos.

Methods. We selected 75 clusters with M ≥ 6 × 10¹⁴ M_⊙ at z = 0.08 − 0.33 from the Planck Sunyaev-Zel’dovich catalogue. Clusters without suitable radio data were observed with the Giant Metrewave Radio Telescope and/or the Jansky Very Large Array to complete the information about the possible presence of diffuse emission. We used archival Chandra X-ray data to derive information on the clusters’ dynamical states.

Results. This observational campaign led to the detection of several cluster-scale diffuse radio sources and candidates that deserve future follow-up observations. Here we summarise their properties and add information resulting from our new observations. For the clusters where we did not detect any hint of diffuse emission, we derived new upper limits to their diffuse flux.

Conclusions. We have built the largest mass-selected (> 80% complete in mass) sample of galaxy clusters with deep radio observations available to date. The statistical analysis of the sample, which includes the connection between radio halos and cluster mergers, the radio power – mass correlation, and the occurrence of radio halos as a function of the cluster mass, will be presented in Paper II.