Cosmic Reionization of the Early Universe

(Multi-scale, Multi-physics Modeling and Petascale Scientific Computing)

We have recently been actively collaborating with researchers from the Laboratory for Computational Astrophysics at the University of California at San Diego, addressing fundamental questions regarding reionization of the early universe following the Big Bang. Modern observational astronomy has offered some glimpses into the earliest precursors of galactic formation, giving rise to debate as to the underlying physical processes that formed our universe. Through this collaboration, we aim to address the core components of this debate, through developing new models for cosmic reionization in an attempt to match computational simulation to telescope observation.

For these studies, we are developing coupled radiation-hydrodynamic-chemical kinetics simulations that will attempt to test some of these modern theories against experimental observation. As with our research efforts in fusion energy and core-collapse supernovae, these models involve the coupling of a large number of physical processes, including the compressible Euler equations for gas motion, nonlinear radiation diffusion equations for multi-frequency radiation transport, chemical kinetics models for tracking the ionization state of primordial elemental species, as well as a model for gravitational acceleration due to star clustering and galactic formation. This problem therefore combines all challenges facing modern scientific computation: consistent modeling of the relevant physical processes, analysis of the well-posedness of the resulting PDE modeling system, the derivation and development of high-fidelity numerical methods for accurately approximating processes at large (cosmic) and ``small'' (solar) scales, and the invention of solution strategies for efficiently solving the resulting PDE model system on some of the largest NSF supercomputers available.

Figure 1:  Numerical Simulaitons of Cosmic Reionization (left) and Cluster Formation (right). Images courtesy of collaborators at the LCA.

In this effort we have been working on nearly all of these fronts: deriving a coupled PDE modeling system that will both capture the dominant physical processes while lending itself to efficient numerical solution; deriving an accurate time-evolution technique for the coupled radiation transport and chemical kinetics processes occurring on multiple time and space scales, and implementing computational algorithms based on these approaches designed to utilize next-generation petascale computing hardware [1, 2].

Figure 2:  Cosmic Reionization using new scalable algorithms. Image courtesy of collaborators at the LCA.

Funding Support

    NSF AAG Grant 0808184 (co-PI; with M. Norman), 2008-2011.

References