1. Center for Theoretical Astrophysics and Cosmology, Institute for Computational Science, University of Zurich, Winterthurerstrasse 190, CH-8057 Zürich, Switzerland
2. Dipartimento di Fisica G. Occhialini, Università degli Studi di Milano–Bicocca, Piazza della Scienza 3, I-20126 Milano, Italy
3. INFN, Sezione Milano–Bicocca, Piazza della Scienza 3, I-20126 Milano, Italy
4. Institut d'Astrophysique de Paris, Sorbonne Universités, UPMC Univ. Paris 06 et CNRS, UMR 7095, 98bis boulevard Arago, F-75014 Paris, France
5. Department of Physics, Queensborough Community College, 222-05 56th Avenue, Bayside, NY 11364, USA
6. Institute of Astronomy, University of Cambridge, Madingley Road, Cambridge CB3 0HA, UK