1. Department of Physics and Astronomy, University of Sheffield, Hounsfield Rd, Sheffield S3 7RH, UK
2. European Organisation for Astronomical Research in the Southern Hemisphere (ESO), Karl-Schwarzschild-Str. 2, D-85748 Garching b. München, Germany
3. Physics Division, Lawrence Berkeley National Laboratory, 1 Cyclotron Road, Berkeley, CA 94720, USA
4. Department of Physics, Florida State University, Tallahassee, FL 32306-4350, USA
5. George P. and Cynthia Woods Mitchell Institute for Fundamental Physics and Astronomy, Texas A&M University
6. Department of Astronomy and McDonald Observatory, The University of Texas at Austin, Austin, TX 78712, USA
7. Institute of Astrophysics, Universidad Católica de Chile, and Millennium Institute of Astrophysics, Santiago, Chile
8. Department of Particle Physics and Astrophysics, Weizmann Institute of Science, Rehovot 76100, Israel