1. Max Planck Institute for Astrophysics, 85748 Garching, Germany
2. Faculty for Physics, Ludwig-Maximilians-Universität, 80539 Munich, Germany
3. Department for Computer Science, Technical University Munich, 85748 Munich, Germany
4. Astrophysics Group, Cavendish Laboratory, J. J. Thomson Avenue, Cambridge CB3 0HE, UK
5. Kavli Institute for Cosmology, Madingley Road, Cambridge CB3 0EZ, UK