1. Department of Physics, University of Bath , Claverton Down, Bath BA2 7AY, UK
2. Department of Astronomy, University of Massachusetts , Amherst, MA 01003, USA
3. Dunlap Institute for Astronomy and Astrophysics, University of Toronto , 50 St. George Street, Toronto, ON M5S 3H4, Canada
4. Cosmic Dawn Center (DAWN) , Copenhagen, Denmark
5. Niels Bohr Institute, University of Copenhagen , Lyngbyvej 2, DK-2100 Copenhagen, Denmark
6. Max-Planck-Institut für Astronomie , Königstuhl 17, D-69117 Heidelberg, Germany
7. Astronomy Department, Yale University , New Haven, CT 06511, USA
8. Max-Planck-Institut für extraterrestrische Physik , Giessenbachstrasse 1, D-85748 Garching, Germany
9. Department for Astrophysical and Planetary Science, University of Colorado , Boulder, CO 80309, USA
10. Department of Physics and Astronomy, University of North Carolina Asheville , 1 University Heights, Asheville, NC 28804, USA
11. Sterrenkundig Observatorium, Universiteit Gent , Krijgslaan 281 S9, B-9000 Gent, Belgium