Scalable Hierarchical Particle Algorithms for Galaxy Formation and Accretion Astrophysics

Investigators

• Wojciech H. Zurek, Jack G. Hills, Warner A. Miller, Michael S. Warren

  Theoretical Astrophysics, Los Alamos National Laboratory

• Melvyn B. Davies

  Theoretical Astrophysics, California Institute of Technology

• John K. Salmon

  Concurrent Supercomputing Facility, California Institute of Technology

• Geoffrey C. Fox

  Northeast Parallel Architectures Center, Syracuse University

• Pablo Laguna

  Department of Astronomy and Astrophysics, The Pennsylvania State University

• Peter J. Quinn

  Mount Stromlo Observatory

Abstract

We will develop parallel, scalable particle codes (N-body, smoothed particle hydrodynamic (SPH), and hybrid) based on hierarchical tree data structures and use them to study astrophysical problems. This work will build on our already successful parallel implementation of a purely gravitational cosmological treecode (which has demonstrated production simulation performance in excess of 5 Gflops on the Intel Touchstone Delta, with $N \sim 10^7$). We shall focus on (i.) dissipationless structure formation on both sub-galactic and large scales, (ii.) use the hybrid N-body/SPH code to study infall of baryons and the origin of the luminous parts of galaxies. We shall also use parallel SPH to study (iii.) tidal disruption of stars in both non-relativistic and general relativistic contexts, and (iv.) accretion onto a rotating black hole. Moreover, we shall, (a.) abstract the relevant features of the parallel tree data structures for use in other applications, (b.) study various approaches to the analysis and visualization of our data. The computational aspects of the project will be carried out entirely on massively parallel processors.

The primary astrophysical objective of our proposal is the understanding of structure formation on sub-galactic to cosmological distance scales. The primary computational objective is the development of scalable parallel hierarchical N-body/SPH codes suitable for addressing these problems. The computational methods can be adapted to other astrophysical problems, and eventually applied to problems in other disciplines.

Introduction

The research suggested here is a natural extension of our ongoing research. It can be divided into five principal categories, each of fundamental importance to astrophysics. The categories are related by their common need for a sophisticated numerical approach and the suitability of gridless particle methods as a key tool:

• The formation of galactic halos in a cosmological context and the dissipationless evolution of stellar systems by the process of galactic mergers and satellite infall.

• The dissipative evolution of the baryonic component of galaxies (in particular, disks of spiral galaxies) via the infall and cooling of gas in collapsing dark matter halos.

• Formation of large scale structure in the Universe, and its relation to observations (including the recently reported cosmic microwave anisotropy).

• Stellar disruption in tidal fields of compact objects, including massive black holes --- a process which may be responsible for ``feeding'' quasars and other active galactic nuclei (AGN).

• Accretion disks, with particular attention to the study of 3-D hydrodynamic flows on curved static backgrounds, such as the Kerr geometry of a rotating black hole (a process thought to power AGN).

• Computer Science Tools that support the hierarchical data structures used in tree codes -- and similar applications such as multilevel vision -- on parallel supercomputers.

Additional Information

• Phase I final report

• Graphics

  Some images and animations of various N-body simulations.

• Publications

  Postscript versions of published papers and preprints.

Elsewhere on the Web

• NSF MetaCenter Science Highlights.

  Studying Galaxy Formation with N-body Simulations and ``Treecodes''

• CSCC 1992 Annual Report.

  N-Body Simulations on the Touchstone Delta.

• CSCC 1994 Annual Report.

  Impact of Shoemaker-Levy 9 with Jupiter.

• CSCC 1994 Annua l Report.

  Fast Particle Algorithms for Computational Fluid Dynamics: Smooth-Particle Hydrodynamics and Vortex Particle Methods.

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