1. Department of Physics and Astronomy, University of Sheffield, Hounsfield Rd, Sheffield S3 7RH, UK
2. Department of Physics and Astronomy, University of Auckland, 38 Princes Street, 1142 Auckland, New Zealand
3. European Organisation for Astronomical Research in the Southern Hemisphere (ESO), Karl-Schwarzschild-Str 2, D-85748 Garching bei München, Germany
4. Physics Division, Lawrence Berkeley National Laboratory, 1 Cyclotron Road, Berkeley, CA 94720, USA
5. Departamento de Astronomia y Astrofisica, Pontificia Universidad Católica de Chile, Casilla 306, Santiago 22, 3580000, Chile
6. Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218, USA
7. Department of Physics, Florida State University, Tallahassee, FL 32306-4350, USA
8. Department of Astronomy, The Ohio State University, 140 West 18th Avenue, Columbus, OH 43210, USA
9. Department of Astronomy and McDonald Observatory, The University of Texas at Austin, Austin, TX 78712, USA