1. School of Mathematics and Physics, University of Surrey , Guildford GU2 7XH , UK
2. Center for Computational Astrophysics, Flatiron Institute , 162 5th Av., New York City, NY 10010 , USA
3. Department of Astronomy, Columbia University , New York, NY 10027 , USA
4. Department of Astronomy, University of Wisconsin–Madison , Madison, WI 53706, USA
5. William H. Miller III Department of Physics and Astronomy, The Johns Hopkins University , Baltimore, MD 21218, USA