The MeerKAT Galaxy Cluster Legacy Survey

I. Survey Overview and Highlights^⋆

¹ Astrophysics Research Centre, University of KwaZulu-Natal, Durban 4041, South Africa
e-mail: k.knowles@ru.ac.za
² Centre for Radio Astronomy Techniques and Technologies, Department of Physics and Electronics, Rhodes University, PO Box 94 Makhanda 6140, South Africa
³ South African Radio Astronomy Observatory, 2 Fir Street, Observatory 7925, South Africa
⁴ National Radio Astronomy Observatory, Charlottesville, VA 22903, USA
⁵ Minnesota Institute for Astrophysics, University of Minnesota, 116 Church St SE, Minneapolis, MN 55455, USA
⁶ Wits Centre for Astrophysics, School of Physics, University of the Witwatersrand, 1 Jan Smuts Avenue, Johannesburg 2050, South Africa
⁷ Department of Physics, University of Pretoria, Hatfield 0028, South Africa
⁸ INAF – Osservatorio Astronomico di Cagliari, Via della Scienza 5, 09047 Selargius, CA, Italy
⁹ Hartebeesthoek Radio Astronomy Observatory, SARAO, Krugersdorp 1740, South Africa
¹⁰ York University, Toronto, ON, Canada
¹¹ Hamburger Sternwarte, Universität Hamburg, Gojenbergsweg 112, 21029 Hamburg, Germany
¹² Department of Astronomy, University of Cape Town, Rondebosch 7700, South Africa
¹³ Centre for Space Research, North-West University, Potchefstroom 2520, South Africa
¹⁴ Department of Physics and Astronomy, Faculty of Physical Sciences, University of Nigeria, Carver Building, 1 University Road, Nsukka, Nigeria
¹⁵ Naval Research Laboratory, Washington, DC 20375, USA
¹⁶ INAF – Istituto di Radioastronomia, Via Gobetti 101, 40129 Bologna, Italy
¹⁷ Argelander-Institut für Astronomie, Universität Bonn, Auf dem Hügel 71, 53121 Bonn, Germany
¹⁸ School of Mathematics, Statistics, and Computer Science, University of KwaZulu-Natal, Westville 3696, South Africa
¹⁹ Department of Physics and Astronomy, University of the Western Cape, Bellville 7535, South Africa
²⁰ Dipartimento di Fisica, Universitá Sapienza, P.le Aldo Moro 2, 00185 Roma, Italy
²¹ African Institute for Mathematical Sciences, 6-8 Melrose Road, Muizenberg 7945, South Africa
²² Inter-University Institute for Data Intensive Astronomy, University of Cape Town, Rondebosch 7700, South Africa
²³ Tellumat (Pty) Ltd., 64-74 White Road, Retreat 7945, South Africa
²⁴ EMSS Antennas, 18 Techno Avenue, Technopark, Stellenbosch 7600, South Africa
²⁵ SKA Observatory, Jodrell Bank, Lower Withington, Macclesfield, Cheshire SK11 9FT, UK
²⁶ Department of Electrical and Electronic Engineering, Stellenbosch University, Stellenbosch 7600, South Africa
²⁷ Oxford Astrophysics, Denys Wilkinson Building, Keble Road, Oxford OX1 3RH, UK
²⁸ , 12 Blaauwklippen Rd, Kirstenhof 7945, South Africa
²⁹ Presidential Infrastructure Coordinating Commission, 77 Meintjies Street, Sunnyside 0001, South Africa
³⁰ Indian Institute of Astrophysics, II Block, Koramangala, Bengaluru 560 034, India
³¹ GEPI, Observatoire de Paris, CNRS, PSL Research University, Université Paris Diderot, 92190 Meudon, France
³² Peralex (Pty) Ltd., 5 Dreyersdal Rd, Bergvliet 7945, South Africa

Received: 7 June 2021
Accepted: 25 October 2021

Abstract

MeerKAT’s large number (64) of 13.5 m diameter antennas, spanning 8 km with a densely packed 1 km core, create a powerful instrument for wide-area surveys, with high sensitivity over a wide range of angular scales. The MeerKAT Galaxy Cluster Legacy Survey (MGCLS) is a programme of long-track MeerKAT L-band (900−1670 MHz) observations of 115 galaxy clusters, observed for ∼6−10 h each in full polarisation. The first legacy product data release (DR1), made available with this paper, includes the MeerKAT visibilities, basic image cubes at ∼8″ resolution, and enhanced spectral and polarisation image cubes at ∼8″ and 15″ resolutions. Typical sensitivities for the full-resolution MGCLS image products range from ∼3−5 μJy beam⁻¹. The basic cubes are full-field and span 2° × 2°. The enhanced products consist of the inner 1.2° × 1.2° field of view, corrected for the primary beam. The survey is fully sensitive to structures up to ∼10′ scales, and the wide bandwidth allows spectral and Faraday rotation mapping. Relatively narrow frequency channels (209 kHz) are also used to provide H I mapping in windows of 0 < z < 0.09 and 0.19 < z < 0.48. In this paper, we provide an overview of the survey and the DR1 products, including caveats for usage. We present some initial results from the survey, both for their intrinsic scientific value and to highlight the capabilities for further exploration with these data. These include a primary-beam-corrected compact source catalogue of ∼626 000 sources for the full survey and an optical and infrared cross-matched catalogue for compact sources in the primary-beam-corrected areas of Abell 209 and Abell S295. We examine dust unbiased star-formation rates as a function of cluster-centric radius in Abell 209, extending out to 3.5 R ₂₀₀. We find no dependence of the star-formation rate on distance from the cluster centre, and we observe a small excess of the radio-to-100 μm flux ratio towards the centre of Abell 209 that may reflect a ram pressure enhancement in the denser environment. We detect diffuse cluster radio emission in 62 of the surveyed systems and present a catalogue of the 99 diffuse cluster emission structures, of which 56 are new. These include mini-halos, halos, relics, and other diffuse structures for which no suitable characterisation currently exists. We highlight some of the radio galaxies that challenge current paradigms, such as trident-shaped structures, jets that remain well collimated far beyond their bending radius, and filamentary features linked to radio galaxies that likely illuminate magnetic flux tubes in the intracluster medium. We also present early results from the H I analysis of four clusters, which show a wide variety of H I mass distributions that reflect both sensitivity and intrinsic cluster effects, and the serendipitous discovery of a group in the foreground of Abell 3365.