[1] Univ Portsmouth, Inst Cosmol & Gravitat, Dennis Sciama Bldg, Portsmouth PO1 3FX, Hants, England
[2] Univ Durham, Inst Computat Cosmol, Dept Phys, South Rd, Durham DH1 3LE, England
[3] Max Planck Inst Extraterr Phys, Postfach 1312, D-85741 Garching, Germany
[4] Univ Durham, Ctr Extragalact Astron, Dept Phys, South Rd, Durham DH1 3LE, England
[5] Pontifica Univ Catolica Chile, Inst Astrofis, Santiago, Chile
[6] Ctr Estudios Fis Cosmos Aragon, Plaza San Juan 1, E-44001 Teruel, Spain