[1] Univ Tsukuba, Ctr Computat Sci, Ten Nodai 1-1-1, Tsukuba, Ibaraki 3058577, Japan
[2] Univ Edinburgh, Inst Astron, Royal Observ, Edinburgh EH9 3HJ, Midlothian, Scotland
[3] Inst Astrofis Canarias, C Via Lactea S-N, Tenerife 38205, Spain
[4] Tohoku Univ, Grad Sch Sci, Astron Inst, Aoba Ku, Sendai, Miyagi 9808578, Japan