[1] CSIC, Inst Ciencies Espai, IEEC, Campus UAB,Caner Can Magrans S-N, E-08193 Cerdanyola Del Valles, Catalonia, Spain
[2] Univ Barcelona, IEEC UB, Inst Ciencies Cosmos ICCUB, Dept Fis Quant & Astrofis, Marti i Franques 1, E-08028 Barcelona, Catalonia, Spain
[3] Univ Nacl Autonoma Mexico, Inst Radioastron & Astrofis, POB-72, Morelia 58090, Michoacan, Mexico
[4] Univ Michigan, Dept Astron, 311 West Hall,1085 S Univ, Ann Arbor, MI 48109 USA
[5] Acad Sinica, Inst Astron & Astrophys, POB 23-141, Taipei 10617, Taiwan
[6] ESO, Karl Schwarzschild Str 2, D-85748 Garching, Germany
[7] Harvard Smithsonian Ctr Astrophys, 60 Garden St, Cambridge, MA 02138 USA
[8] Nanjing Univ, Sch Astron & Space Sci, 163 Xianlin Ave, Nanjing 210023, Jiangsu, Peoples R China
[9] Nanjing Univ, Minist Educ, Key Lab Modern Astron & Astrophys, Nanjing 210023, Jiangsu, Peoples R China