[1] Univ Leeds, Sch Phys & Astron, Leeds LS2 9JT, W Yorkshire, England
[2] Univ Manchester, Sch Phys & Astron, Jodrell Bank Ctr Astrophys, Manchester M13 9PL, Lancs, England
[3] Univ Sydney, Sydney Inst Astron SiFA, Sydney, NSW 2006, Australia
[4] Natl Radio Astron Observ, Charlottesville, VA 22903 USA
[5] CSIRO Astron & Space Sci, Epping, NSW 1710, Australia
[6] Max Planck Inst Radioastron, D-53121 Bonn, Germany
[7] Natl Radio Astron Observ, Array Operat Ctr, Socorro, NM 87801 USA
[8] Univ Wisconsin, Dept Astron, Madison, WI 53706 USA
[9] Natl Res Council Canada, Herzberg Inst Astrophys, Domin Radio Astrophys Observ, Penticton, BC V2A 6J9, Canada
[10] Univ Southampton, Sch Phys & Astron, Southampton SO17 1BJ, Hants, England
[11] Univ Hertfordshire, Sci & Technol Res Inst, Hatfield AL10 9AB, Herts, England
[12] CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA
[13] Boston Univ, Dept Astron, Boston, MA 02215 USA
[14] Univ Nacl Autonoma Mexico, Ctr Radioastron & Astrofis, Morelia 58090, Michoacan, Mexico
[15] Univ Jaen, Dept Fis, EPSJ, E-23071 Jaen, Spain
[16] Liverpool John Moores Univ, Astrophys Res Inst, Birkenhead CH41 1LD, Merseyside, England
[17] Univ Maryland, Dept Astron, College Pk, MD 20742 USA
[18] Univ Hawaii, Inst Astron, Honolulu, HI 96822 USA
[19] Univ Barcelona UB IEEC, Dept Astron & Meteorol, E-08028 Barcelona, Spain
[20] Univ Barcelona UB IEEC, ICC, E-08028 Barcelona, Spain
[21] Sq Kilometre Array South Africa, ZA-7405 Cape Town, Western Cape, South Africa
[22] INAF Osservatorio Astrofis Catania, I-95123 Catania, Italy