[1] Univ Chicago, Ctr Cosmol Phys, Chicago, IL 60637 USA
[2] Univ Chicago, Dept Astron & Astrophys, Chicago, IL 60637 USA
[3] Ohio State Univ, Dept Astron, Columbus, OH 43210 USA
[4] CALTECH, Dept Astron, Pasadena, CA 91125 USA
[5] Univ Durham, Inst Computat Cosmol, Durham DH1 3LE, England
[6] Univ Arizona, Steward Observ, Tucson, AZ 85721 USA
[7] Univ Massachusetts, Dept Phys & Astron, Amherst, MA 01003 USA
[8] Observ Lyon, F-69230 St Genis Laval, France