1. National Astronomical Observatories, Chinese Academy of Sciences , Beijing 100101 , China
2. School of Astronomy and Space Science, University of Chinese Academy of Sciences , Beijing 100049 , China
3. Institute for Frontiers in Astronomy and Astrophysics, Beijing Normal University , Beijing 102206 , China
4. Institute for Computational Cosmology, Department of Physics, Durham University , Science Laboratories, South Road, Durham DH1 3LE , UK
5. Max-Planck Institute for Astrophysics , Karl-Schwarzschild Str 1, D-85748 Garching , Germany