GADGET
Encyclopedia
GADGET is a freely available code for cosmological N-body/SPH simulations
written by Volker Springel at the Max Planck Institute for Astrophysics
. The name is an acronym of "GAlaxies with Dark matter and Gas intEracT".
scheme for long-range gravitational forces) and represents fluids by means of smoothed particle hydrodynamics
(SPH). The code can be used for studies of isolated systems, or for simulations that include the cosmological expansion of space, both with or without periodic boundary conditions. In all these types of simulations, GADGET follows the evolution of a self-gravitating collisionless N-body
system, and allows gas dynamics
to be optionally included. Both the force computation and the time stepping of GADGET are fully adaptive, with a dynamic range which is, in principle, unlimited.
GADGET can therefore be used to address a wide array of astrophysically interesting problems, ranging from colliding and merging galaxies
, to the formation of large-scale structure in the universe. With the inclusion of additional physical processes such as radiative cooling and heating, GADGET can also be used to study the dynamics of the gaseous intergalactic medium, or to address star formation
and its regulation by feedback processes.
. Later, the code was continuously improved during postdocs of Volker Springel at the Harvard-Smithsonian Center for Astrophysics
and the Max Planck Institute, in collaboration with Simon White and Lars Hernquist
.
The second public version (GADGET-2, released in May 2005) contains most of these improvements, except for the numerous physics modules developed for the code that go beyond gravity and ordinary gas-dynamics. The most important changes lie in a new time integration model, a new tree-code module, a new communication scheme for gravitational and SPH forces, a new domain decomposition strategy, a novel SPH formulation based on entropy
as independent variable, and finally, in the addition of the TreePM functionality.
N-body simulation
An N-body simulation is a simulation of a dynamical system of particles, usually under the influence of physical forces, such as gravity . In cosmology, they are used to study processes of non-linear structure formation such as the process of forming galaxy filaments and galaxy halos from dark...
written by Volker Springel at the Max Planck Institute for Astrophysics
Max Planck Institute for Astrophysics
The Max Planck Institute for Astrophysics is a Max Planck Institute, located in Garching, near Munich, Bavaria, Germany. It was founded as Max Planck Institute for Physics and Astrophysics in 1958 and split up into the Max Planck Institute for Astrophysics and the Max Planck Institute for Physics...
. The name is an acronym of "GAlaxies with Dark matter and Gas intEracT".
Description
GADGET computes gravitational forces with a hierarchical tree algorithm (optionally in combination with a particle-meshEwald summation
Ewald summation, named after Paul Peter Ewald, is a method for computing the interaction energies of periodic systems , particularly electrostatic energies. Ewald summation is a special case of the Poisson summation formula, replacing the summation of interaction energies in real space with an...
scheme for long-range gravitational forces) and represents fluids by means of smoothed particle hydrodynamics
Smoothed particle hydrodynamics
Smoothed-particle hydrodynamics is a computational method used for simulating fluid flows. It has been used in many fields of research, including astrophysics, ballistics, volcanology, and oceanography...
(SPH). The code can be used for studies of isolated systems, or for simulations that include the cosmological expansion of space, both with or without periodic boundary conditions. In all these types of simulations, GADGET follows the evolution of a self-gravitating collisionless N-body
N-body problem
The n-body problem is the problem of predicting the motion of a group of celestial objects that interact with each other gravitationally. Solving this problem has been motivated by the need to understand the motion of the Sun, planets and the visible stars...
system, and allows gas dynamics
Gas dynamics
Gas dynamics is a branch of fluid dynamics concerned with studying the motion of gases and its consequent effects. Gas dynamics combines the principles of fluid mechanics and thermodynamics...
to be optionally included. Both the force computation and the time stepping of GADGET are fully adaptive, with a dynamic range which is, in principle, unlimited.
GADGET can therefore be used to address a wide array of astrophysically interesting problems, ranging from colliding and merging galaxies
Galaxy merger
Galaxy mergers can occur when two galaxies collide. They are the most violent type of galaxy interaction. Although galaxy mergers do not involve stars or star systems actually colliding, due to the vast distances between stars in most circumstances, the gravitational interactions between galaxies...
, to the formation of large-scale structure in the universe. With the inclusion of additional physical processes such as radiative cooling and heating, GADGET can also be used to study the dynamics of the gaseous intergalactic medium, or to address star formation
Star formation
Star formation is the process by which dense parts of molecular clouds collapse into a ball of plasma to form a star. As a branch of astronomy star formation includes the study of the interstellar medium and giant molecular clouds as precursors to the star formation process and the study of young...
and its regulation by feedback processes.
History
The first public version (GADGET-1, released in March 2000) was created as part of Volker's PhD project under the supervision of Simon WhiteSimon White
Professor Simon David Manton White, FRS is a British astrophysicist. He is one of four directors at the Max Planck Institute for Astrophysics.- Life :...
. Later, the code was continuously improved during postdocs of Volker Springel at the Harvard-Smithsonian Center for Astrophysics
Harvard-Smithsonian Center for Astrophysics
The Harvard–Smithsonian Center for Astrophysics is one of the largest and most diverse astrophysical institutions in the world, where scientists carry out a broad program of research in astronomy, astrophysics, earth and space sciences, and science education...
and the Max Planck Institute, in collaboration with Simon White and Lars Hernquist
Lars Hernquist
Lars Hernquist is a theoretical astrophysicist and Mallinckrodt Professor of Astrophysics at the Harvard-Smithsonian Center for Astrophysics. He is best known for his research on dynamical processes in cosmology and galaxy formation/galaxy evolution.-Research:...
.
The second public version (GADGET-2, released in May 2005) contains most of these improvements, except for the numerous physics modules developed for the code that go beyond gravity and ordinary gas-dynamics. The most important changes lie in a new time integration model, a new tree-code module, a new communication scheme for gravitational and SPH forces, a new domain decomposition strategy, a novel SPH formulation based on entropy
Entropy
Entropy is a thermodynamic property that can be used to determine the energy available for useful work in a thermodynamic process, such as in energy conversion devices, engines, or machines. Such devices can only be driven by convertible energy, and have a theoretical maximum efficiency when...
as independent variable, and finally, in the addition of the TreePM functionality.