1. Centre for Extragalactic Astronomy, Department of Physics, Durham University, Durham DH1 3LE, UK
2. Centre for Astrophysics Research, School of Physics, Astronomy and Mathematics, University of Hertfordshire, Hatfield AL10 9AB, UK
3. Institute of Astronomy and Astrophysics, No. 1, Section 4, Academia Sinica, Roosevelt Rd., Taipei 10617, Taiwan
4. Purple Mountain Observatory, China Academy of Sciences, 2 West Beijing Road, Nanjing 210008, China
5. School of Physics and Astronomy, University of Nottingham, University Park, Nottingham, NG7 2RD, UK
6. European Southern Observatory, Karl Schwarzschild Strasse 2, 85748 Garching, Germany
7. Institute for Astronomy, University of Edinburgh, Royal Observatory, Blackford Hill, Edinburgh EH9 3HJ, UK
8. Department of Physics and Astronomy, University of Leicester,University Road, Leicester LE1 7RH, UK
9. Department of Physics and Atmospheric Science, Dalhousie University Halifax, NS B3H 3J5, Canada
10. Research School of Astronomy and Astrophysics, The Australian National University, Canberra ACT 2611, Australia
11. Department of Physics and Astronomy, University of Hawaii, 2505 Correa Road, Honolulu, HI 96822, USA
12. Institute for Astronomy, 2680 Woodlawn Drive, University of Hawaii, Honolulu, HI 96822, USA
13. Leiden Observatory, Leiden University, P.O. box 9513, NL-2300 RA Leiden, the Netherlands
14. Department of Physics and Astronomy, Colby College, Waterville, ME 04961, USA
15. Astronomical Observatory Institute, Faculty of Physics, Adam Mickiewicz University, ul. Słoneczna 36, 60-286 Poznań, Poland
16. Instututo de Astronomía sede Ensenada, Universidad Nacional Autónoma de México, Ensenada, 22860, México
17. Department of Physics and Astronomy, University of British Columbia, 6224 Agricultural Road, Vancouver, BC V6T 1Z1, Canada
18. The University of Manchester, Oxford Road, Manchester, M13 9PL, UK
19. Department of Physics, Lancaster University, Lancaster, LA1 4YB, UK
20. Max-Planck-Institut für Radioastronomie, Auf dem Hügel 69 D-53121 Bonn, Germany