1. National Astronomy Observatories, Chinese Academy of Science, Beijing, 100101, P. R. China
2. Institute of Cosmology & Gravitation, University of Portsmouth, Dennis Sciama Building, Portsmouth PO1 3FX, UK
3. Leibniz-Institut für Astrophysik Potsdam (AIP), An der Sternwarte 16, D-14482 Potsdam, Germany
4. Instituto de Astrofísica de Canarias (IAC), C/Vía Láctea, s/n, E-38200, La Laguna, Tenerife, Spain
5. Departamento Astrofísica, Universidad de La Laguna (ULL), E-38206 La Laguna, Tenerife, Spain
6. Tsinghua Center of Astrophysics and Department of Physics, Tsinghua University, Beijing 100084, P. R. China
7. Campus of International Excellence UAM+CSIC, Cantoblanco, E-28049 Madrid, Spain
8. Departamento de Física Teórica, Universidad Autónoma de Madrid, Cantoblanco, E-28049, Madrid, Spain