1. Department of Physics, University of Milano – Bicocca , Piazza della Scienza 3, I-20126 Milano, Italy
2. Institut für Physik und Astronomie, Universität Potsdam , Haus 28, Karl-Liebknecht-Str. 24/25, D-14476 Potsdam, Germany
3. INFN, Sezione di Milano-Bicocca , Piazza della Scienza 3, I-20126 Milano, Italy
4. INAF - Osservatorio Astronomico di Brera , via Brera 20, I-20121 Milano, Italy
5. Max-Planck-Institut für Radioastronomie , Auf dem Hügel 69, D-53121 Bonn, Germany
6. Institute of Astrophysics, Foundation for Research & Technology – Hellas (FORTH) , GR-70013 Heraklion, Greece
7. INAF - Osservatorio Astronomico di Cagliari , via della Scienza 5, I-09047 Selargius (Cagliari), Italy
8. Kavli Institute for Astronomy and Astrophysics, Peking University , 100871 Beijing, China
9. Observatoire Radioastronomique de Nançay, Observatoire de Paris, Université PSL, Université d’Orléans , CNRS, F-18330 Nançay, France
10. Laboratoire de Physique et Chimie de l’Environnement et de l’Espace, Université d’Orléans/CNRS , F-45071 Orléans Cedex 02, France
11. Jodrell Bank Centre for Astrophysics, School of Physics and Astronomy, The University of Manchester , Manchester M13 9PL, UK
12. Canadian Institute for Theoretical Astrophysics, University of Toronto , 60 Saint George Street, Toronto, ON M5S 3H8, Canada
13. LUTH, Observatoire de Paris, Université PSL, Université Paris Cité , CNRS, F-92195 Meudon, France
14. ASTRON, the Netherlands Institute for Radio Astronomy , Postbus 2, NL-7990 AA Dwingeloo, the Netherlands
15. Department of Astrophysics/IMAPP, Radboud University , PO Box 9010, NL-6500 GL Nijmegen, the Netherlands