1. Department of Physics and Astronomy, University of Southern California, Los Angeles, CA 90089-0484, USA
2. Division of Physics, Math, and Astronomy, California Institute of Technology, Pasadena, CA 91125, USA
3. Kavli Institute for Particle Astrophysics and Cosmology, Stanford University, Stanford, CA 94305-4085, USA
4. ESO - European Organization for Astronomical Research in the Southern hemisphere, Karl-Schwarzschild-Str. 2, D-85748 Garching b. Munchen, Germany
5. INAF, Osservatorio Astronomico di Trieste, via Tiepolo 11, I-34131 Trieste, Italy
6. Department of Physics, McGill University, 3600 Rue University, Montreal, QC H3A 2T8, Canada