1. CAS Key Laboratory for Optical Astronomy, National Astronomical Observatories, Chinese Academy of Sciences , Beijing 100012 , China
2. Department of Astronomy, Kyoto University , Kitashirakawa-Oiwake-cho, Sakyo-ku, Kyoto 606-8502 , Japan
3. Department of Physics, Technion – Israel Institute of Technology , Haifa 32000 , Israel