1. National Astronomical Observatories, Chinese Academy of Sciences, 20A Datun Road, Chaoyang District, Beijing 100101, China
2. CSIRO Astronomy and Space Science, P.O. Box 76, Epping, NSW 1710, Australia
3. University of Chinese Academy of Sciences, Beijing 100049, China
4. Xinjiang Astronomical Observatory, 150, Science-1 Street, Urumqi, 830011 Xinjiang, China
5. Key Laboratory of Radio Astronomy, Chinese Academy of Sciences, 150 Science 1-Street, Urumqi, 830011 Xinjiang, China
6. Xinjiang Key Laboratory of Radio Astrophysics, 150 Science 1-Street, Urumqi, 830011 Xinjiang, China
7. Victoria University of Wellington, P.O. Box 600, Wellington 6140, New Zealand
8. Max-Planck Institut für Radioastronomie, Auf dem Hügel 69, D-53121 Bonn, Germany
9. National Research Council Canada, Herzberg Research Centre for Astronomy and Astrophysics, Dominion Radio Astrophysical Observatory, P.O. Box 248, Penticton, BC V2A 6J9, Canada
10. Guizhou Provincial Key Laboratory of Radio Astronomy and Data Processing, Guizhou Normal University, Guiyang 550001, China
11. School of Physics and Electronic Science, Guizhou Normal University, Guiyang 550001, China
12. Kavli Institute for Astronomy and Astrophysics, Peking University, Beijing 100871, China
13. Department of Astronomy, School of Physics, Peking University, Beijing 100871, China
14. Purple Mountain Observatory, Chinese Academy of Sciences, Nanjing 210008, China
15. International Centre for Radio Astronomy Research, University of Western Australia, Crawley, WA 6009, Australia
16. Jodrell Bank Center for Astrophysics, University of Manchester, Alan Turing Building, Oxford Road, Manchester M13 9PL, UK
17. School of Astronomy and Space Science, Nanjing University, 163 Xianlin Avenue, Nanjing 210023, China