1. University of Illinois at Urbana-Champaign, National Center for Supercomputing Applications, Urbana, IL, USA
2. National Center for Supercomputing Applications, University of Illinois at Urbana-Champaign, Urbana, IL, USA
3. National Center for Supercomputing Applications, Department of Astronomy, University of Illinois at Urbana-Champaign, Urbana, IL, USA
4. Department of Physics, University of Illinois at Urbana-Champaign, Urbana, IL, USA