1. Astrophysics, Department of Physics, University of Oxford , Keble Road, Oxford, OX1 3RH , UK
2. Department of Physics and Astronomy, University of the Western Cape , Robert Sobukwe Road, 7535 Bellville, Cape Town , South Africa
3. Inter-University Institute for Data Intensive Astronomy (IDIA), University of the Western Cape , Robert Sobukwe Road, 7535 Bellville, Cape Town , South Africa
4. Institute for Astronomy, Royal Observatory Edinburgh , Blackford Hill, Edinburgh, EH9 3HJ , UK
5. Centre for Radio Astronomy Techniques and Technologies, Department of Physics and Electronics, Rhodes University , PO Box 94, Makhanda 6140 , South Africa
6. South African Radio Astronomy Observatory , 2 Fir Street, Black River Park, Observatory, Cape Town 7925 , South Africa
7. The Inter-University Institute for Data Intensive Astronomy (IDIA), Department of Astronomy, University of Cape Town , Private Bag X3, Rondebosch 7701 , South Africa
8. International Centre for Radio Astronomy Research, Curtin University , Bentley, WA 6102 , Australia
9. University Observatory, Faculty of Physics , Ludwig-Maximilians-Universität, Scheinerstr. 1, D-81679 Munich , Germany
10. Department of Astronomy, University of Cape Town , 7701 Rondebosch, Cape Town , South Africa
11. INAF - Istituto di Radioastronomia , via Gobetti 101, I-40129 Bologna , Italy
12. Centre for Extragalactic Astronomy, Department of Physics, Durham University , Durham, DH1 3LE , UK
13. Institute for Computational Cosmology, Department of Physics, Durham University , Durham, DH1 3LE , UK
14. Jodrell Bank Centre for Astrophysics, University of Manchester , Oxford Road, Manchester, M13 9PL , UK
15. Instituto de Astrofísica e Ciências do Espaço, Universidade de Lisboa , OAL, Tapada da Ajuda, PT1349-018 Lisboa , Portugal
16. Departamento de Física, Faculdade de Ciências, Universidade de Lisboa , Edifício C8, Campo Grande, PT1749-016 Lisboa , Portugal
17. Purple Mountain Observatory and Key Laboratory for Radio Astronomy, Chinese Academy of Sciences , Nanjing 210023 , China
18. School of Astronomy and Space Science, University of Science and Technology of China , Hefei, Anhui, 230026 , China
19. Physics Department, University of Johannesburg , 5 Kingsway Ave, Rossmore, Johannesburg 2092 , South Africa
20. South African Astronomical Observatory , PO Box 9, Observatory 7935, Cape Town , South Africa
21. A&A, Department of Physics, Faculty of Sciences, University of Antananarivo , B.P. 906, Antananarivo 101 , Madagascar
22. Centre for Astrophysics Research, University of Hertfordshire , College Lane, Hatfield, AL10 9AB , UK