1. Department of Physics and Astronomy, University of California , Riverside, 900 University Avenue, Riverside, CA 92521, USA
2. Steward Observatory, University of Arizona , 933 N Cherry Ave, Tucson, AZ 85721, USA
3. Physics & Astronomy Department, University of California , Los Angeles, 430 Portola Plaza, Los Angeles, CA 90095, USA
4. Department of Physics and Astronomy, University of California , Davis, One Shields Ave, Davis, CA 95616, USA
5. Kavli Institute for Particle Astrophysics & Cosmology , PO Box 2450, Stanford University, Stanford, CA 94305, USA
6. Max-Planck-Institut für extraterrestrische Physik (MPE) , Giessenbachstr 1, D-85748 Garching, Germany
7. Astronomy Department, University of California , Berkeley, Berkeley, CA 94720, USA
8. Leiden Observatory, Leiden University , PO Box 9513, NL-2300 RA Leiden, the Netherlands
9. Center for Astrophysics and Space Sciences, Department of Physics, University of California , San Diego, 9500 Gilman Dr., La Jolla, CA 92093-0424, USA