[1] Kagoshima Univ, Grad Sch Sci & Engn, Kagoshima 8900065, Japan
[2] Chinese Acad Sci, Natl Astron Observ, Yunnan Observ, Kunming 650011, Yunnan, Peoples R China
[3] Univ Hong Kong, Dept Phys, Hong Kong, Hong Kong, Peoples R China
[4] Natl Astron Observ, ALMA Project Off, Tokyo 1818588, Japan
[5] Natl Astron Observ, Nobeyama Radio Observ, Minamisa Ku, Minamimaki, Nagano 3841305, Japan
[6] Univ Calgary, Dept Phys & Astron, Calgary, AB T2N 1N4, Canada