[1] Chinese Acad Sci, Shanghai Astron Observ, Key Lab Res Galaxies & Cosmol, 80 Nandan Rd, Shanghai 200030, Peoples R China
[2] Univ Chinese Acad Sci, 19A Yuquan Rd, Beijing 100049, Peoples R China
[3] Zhejiang Univ, Dept Phys, Zhejiang Inst Modern Phys, 38 Zheda Rd, Hangzhou 310027, Peoples R China
[4] Chinese Acad Sci, Shanghai Astron Observ, 80 Nandan Rd, Shanghai 200030, Peoples R China
[5] Chinese Acad Sci, Key Lab Radio Astron, Nanjing 210008, Peoples R China
[6] Xiamen Univ, Dept Astron, Xiamen 361005, Fujian, Peoples R China