ECCA Software

Baryonic structure formation

The gravitational equations are evolved for a collisionless gas using a Particle-Mesh solver on a Cartesian grid (Meiksin & White 2001). The code is coupled to a radiative transfer code PMRT using a probabilistic method to represent absorption of photons based on the photon-conserving algorithm of Abel, Norman & Madau (1999, ApJ, 523, 66), extended to include helium by Bolton, Meiksin & White (2004). The code is described in Tittley & Meiksin (2006).Both the gravitational and radiative modules are coded in C and parallelised using a message passing interface (MPI).

Recently we have merged the radiative transfer algorithm with the Adaptive Mesh Refinement numerical hydrodynamics code Enzo  (Bryan & Norman 1997; O'Shea, Bryan, Bordner, Norman, Abel, Harkness, & Kritsuk 2004), and are currently running tests of the combined code EnzoRT.

A Java GUI that computes the amount of intergalactic extinction due to scattering and absorption by neutral hydrogen in the IGM and its effect on galaxy colours is available here. A tarball for the code may be downloaded from tarball.

Planet formation

The code used is a combined gravity-hydrodynamics scheme. The equations of hydrodynamics are evolved using Smoothed Particle Hydrodynamics (SPH). The gravitational equations are evolved using a tree structure to compute the gravitational forces and the nearest neighbours of particles. Particles are advanced with individual timesteps, resulting in a huge computational savings for problems involving a wide range of dynamical time scales. The code is in Fortran 77 and parallelised using OpenMP. The code is described in Bate, Bonnell & Price (1995).

Compact objects

The equations of hydrodynamics are evolved using a shock-capturing, explicit, finite difference algorithm, the Piecewise Parabolic Method (PPM). The Newtonian potential of all matter on the grid is computed using Fast-Fourier Transform (FFT) routines. Gravitational wave emission and back-reaction are implemented in a post-Newtonian approximation. The equations are solved on multiply nested and refined Cartesian grids designed to focus on the regions requiring short time scale and high spatial resolution. Both the Lattimer & Swesty and the Shen et al. equations of state are included, as is neutrino emission. Neutrino-antineutrino annihilation is handled in a post-processing stage. The code is written in Fortran 77 and parallelised using OpenMP. A short description of the numerical procedures, initial conditions and results can be found in an extended abstract (gzip'd postscript, 37KB), which is a contribution to the Proceedings of the 17th Texas Symposium (Munich, Dec.11-17 1994).

Dense stellar systems

The work in this area uses standard N-body algorithms (the Aarseth code  N-Body and the Starlab package) and also an adaptation of the Warsaw Monte Carlo code of Mirek Giersz ( 2006, MNRAS, 371, 484:  "Monte Carlo simulations of star clusters - III. A million-body star cluster").