1. The Oskar Klein Centre for Cosmoparticle Physics, SE-106 91 Stockholm, Sweden
2. Department of Physics, KTH Royal Institute of Technology, AlbaNova, SE-106 91 Stockholm, Sweden
3. Astrophysics Group, Imperial College London, Blackett Laboratory, Prince Consort Road, London SW7 2AZ, UK
4. Statistics Section, Department of Mathematics, Imperial College London, London SW7 2AZ, UK
5. Department of Astronomy, Stockholm University, AlbaNova, SE-106 91 Stockholm, Sweden