Computational astrophysics

Last updated

A computer simulation of a star falling into a black hole in the process of forming an accretion disk

Computational astrophysics refers to the methods and computing tools developed and used in astrophysics research. Like computational chemistry or computational physics, it is both a specific branch of theoretical astrophysics and an interdisciplinary field relying on computer science, mathematics, and wider physics. Computational astrophysics is most often studied through an applied mathematics or astrophysics programme at PhD level.

Contents

Well-established areas of astrophysics employing computational methods include magnetohydrodynamics, astrophysical radiative transfer, stellar and galactic dynamics, and astrophysical fluid dynamics. A recently developed field with interesting results is numerical relativity.

Research

Many astrophysicists use computers in their work, and a growing number of astrophysics departments now have research groups specially devoted to computational astrophysics. Important research initiatives include the US Department of Energy (DoE) SciDAC collaboration for astrophysics [1] and the now defunct European AstroSim collaboration. [2] A notable active project is the international Virgo Consortium, which focuses on cosmology.

In August 2015 during the general assembly of the International Astronomical Union a new commission C.B1 on Computational Astrophysics was inaugurated, therewith recognizing the importance of astronomical discovery by computing.

Important techniques of computational astrophysics include particle-in-cell (PIC) and the closely related particle-mesh (PM), N-body simulations, Monte Carlo methods, as well as grid-free (with smoothed particle hydrodynamics (SPH) being an important example) and grid-based methods for fluids. In addition, methods from numerical analysis for solving ODEs and PDEs are also used.

Simulation of astrophysical flows is of particular importance as many objects and processes of astronomical interest such as stars and nebulae involve gases. Fluid computer models are often coupled with radiative transfer, (Newtonian) gravity, nuclear physics and (general) relativity to study highly energetic phenomena such as supernovae, relativistic jets, active galaxies and gamma-ray bursts [3] and are also used to model stellar structure, planetary formation, evolution of stars and of galaxies, and exotic objects such as neutron stars, pulsars, magnetars and black holes. [4] Computer simulations are often the only means to study stellar collisions, galaxy mergers, as well as galactic and black hole interactions. [5] [6]

In recent years the field has made increasing use of parallel and high performance computers. [7]

Tools

Computational astrophysics as a field makes extensive use of software and hardware technologies. These systems are often highly specialized and made by dedicated professionals, and so generally find limited popularity in the wider (computational) physics community.

Hardware

Like other similar fields, computational astrophysics makes extensive use of supercomputers and computer clusters . Even on the scale of a normal desktop it is possible to accelerate the hardware. Perhaps the most notable such computer architecture built specially for astrophysics is the GRAPE (gravity pipe) in Japan.

As of 2010, the biggest N-body simulations, such as DEGIMA, do general-purpose computing on graphics processing units. [8]

Software

Many codes and software packages, exist along with various researchers and consortia maintaining them. Most codes tend to be n-body packages or fluid solvers of some sort. Examples of n-body codes include ChaNGa, MODEST, [9] nbodylab.org [10] and Starlab. [11]

For hydrodynamics there is usually a coupling between codes, as the motion of the fluids usually has some other effect (such as gravity, or radiation) in astrophysical situations. For example, for SPH/N-body there is GADGET and SWIFT; [12] for grid-based/N-body RAMSES, [13] ENZO, [14] FLASH, [15] and ART. [16]

AMUSE , [17] takes a different approach (called Noah's Ark [18] ) than the other packages by providing an interface structure to a large number of publicly available astronomical codes for addressing stellar dynamics, stellar evolution, hydrodynamics and radiative transport.

See also

Related Research Articles

In astronomy, dark matter is a hypothetical form of matter that appears not to interact with light or the electromagnetic field. Dark matter is implied by gravitational effects which cannot be explained by general relativity unless more matter is present than can be seen. Such effects occur in the context of formation and evolution of galaxies, gravitational lensing, the observable universe's current structure, mass position in galactic collisions, the motion of galaxies within galaxy clusters, and cosmic microwave background anisotropies.

The study of galaxy formation and evolution is concerned with the processes that formed a heterogeneous universe from a homogeneous beginning, the formation of the first galaxies, the way galaxies change over time, and the processes that have generated the variety of structures observed in nearby galaxies. Galaxy formation is hypothesized to occur from structure formation theories, as a result of tiny quantum fluctuations in the aftermath of the Big Bang. The simplest model in general agreement with observed phenomena is the Lambda-CDM model—that is, that clustering and merging allows galaxies to accumulate mass, determining both their shape and structure. Hydrodynamics simulation, which simulates both baryons and dark matter, is widely used to study galaxy formation and evolution.

<span class="mw-page-title-main">Globular cluster</span> Spherical collection of stars

A globular cluster is a spheroidal conglomeration of stars that is bound together by gravity, with a higher concentration of stars towards their centers. They can contain anywhere from tens of thousands to many millions of member stars, all orbiting in a stable, compact formation. Globular clusters are similar in form to dwarf spheroidal galaxies, and the distinction between the two is not always clear. Their name is derived from Latin globulus. Globular clusters are occasionally known simply as "globulars".

<span class="mw-page-title-main">Extragalactic astronomy</span> Study of astronomical objects outside the Milky Way Galaxy

Extragalactic astronomy is the branch of astronomy concerned with objects outside the Milky Way galaxy. In other words, it is the study of all astronomical objects which are not covered by galactic astronomy.

<span class="mw-page-title-main">Astrophysics</span> Subfield of astronomy

Astrophysics is a science that employs the methods and principles of physics and chemistry in the study of astronomical objects and phenomena. As one of the founders of the discipline, James Keeler, said, Astrophysics "seeks to ascertain the nature of the heavenly bodies, rather than their positions or motions in space–what they are, rather than where they are." Among the subjects studied are the Sun, other stars, galaxies, extrasolar planets, the interstellar medium and the cosmic microwave background. Emissions from these objects are examined across all parts of the electromagnetic spectrum, and the properties examined include luminosity, density, temperature, and chemical composition. Because astrophysics is a very broad subject, astrophysicists apply concepts and methods from many disciplines of physics, including classical mechanics, electromagnetism, statistical mechanics, thermodynamics, quantum mechanics, relativity, nuclear and particle physics, and atomic and molecular physics.

The Sunyaev–Zeldovich effect is the spectral distortion of the cosmic microwave background (CMB) through inverse Compton scattering by high-energy electrons in galaxy clusters, in which the low-energy CMB photons receive an average energy boost during collision with the high-energy cluster electrons. Observed distortions of the cosmic microwave background spectrum are used to detect the disturbance of density in the universe. Using the Sunyaev–Zeldovich effect, dense clusters of galaxies have been observed.

The Lambda-CDM, Lambda cold dark matter or ΛCDM model is a mathematical model of the Big Bang theory with three major components:

  1. a cosmological constant denoted by lambda (Λ) associated with dark energy,
  2. the postulated cold dark matter, and
  3. ordinary matter.
<i>N</i>-body simulation Simulation of a dynamical system of particles

In physics and astronomy, an N-body simulation is a simulation of a dynamical system of particles, usually under the influence of physical forces, such as gravity. N-body simulations are widely used tools in astrophysics, from investigating the dynamics of few-body systems like the Earth-Moon-Sun system to understanding the evolution of the large-scale structure of the universe. In physical cosmology, N-body simulations are used to study processes of non-linear structure formation such as galaxy filaments and galaxy halos from the influence of dark matter. Direct N-body simulations are used to study the dynamical evolution of star clusters.

Lauro Moscardini is an Italian astrophysicist and cosmologist. Moscardini has studied N-body cosmological simulations with non-Gaussian initial conditions. The research activity is mainly focussed in the field of theoretical and observational cosmology, in particular with the application of numerical techniques in astrophysics and the study of the formation of large cosmic structures. Moscardini's research is a mixture of observations and building models of large scale structures in the universe.

<span class="mw-page-title-main">Galaxy merger</span> Merger whereby at least two galaxies collide

Galaxy mergers can occur when two galaxies collide. They are the most violent type of galaxy interaction. The gravitational interactions between galaxies and the friction between the gas and dust have major effects on the galaxies involved. The exact effects of such mergers depend on a wide variety of parameters such as collision angles, speeds, and relative size/composition, and are currently an extremely active area of research. Galaxy mergers are important because the merger rate is a fundamental measurement of galaxy evolution. The merger rate also provides astronomers with clues about how galaxies bulked up over time.

Computational magnetohydrodynamics (CMHD) is a rapidly developing branch of magnetohydrodynamics that uses numerical methods and algorithms to solve and analyze problems that involve electrically conducting fluids. Most of the methods used in CMHD are borrowed from the well established techniques employed in Computational fluid dynamics. The complexity mainly arises due to the presence of a magnetic field and its coupling with the fluid. One of the important issues is to numerically maintain the (conservation of magnetic flux) condition, from Maxwell's equations, to avoid the presence of unrealistic effects, namely magnetic monopoles, in the solutions.

<span class="mw-page-title-main">GADGET</span> Computer software for cosmological simulations

GADGET is free software 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". It is released under the GNU GPL. It can be used to study for example galaxy formation and dark matter.

<span class="mw-page-title-main">David Merritt</span>

David Roy Merritt is an American astrophysicist.

<span class="mw-page-title-main">Astromundus</span>

Astromundus was a 2-years Erasmus Mundus masters course in Astronomy and Astrophysics. It was offered by a consortium of 5 partner universities of four different European countries. Partner universities were University of Innsbruck in Austria, University of Padova and University of Rome Tor Vergata in Italy, University of Göttingen in Germany and University of Belgrade in Serbia. Belgrade was a third country partner of this consortium.

The University of California High-Performance AstroComputing Center (UC-HiPACC) based at the University of California at Santa Cruz (UCSC) is a consortium of nine University of California campuses and three Department of Energy laboratories. The consortium's goal is to support and facilitate original research and education in computational astrophysics and to engage in public outreach and education.

The Illustris project is an ongoing series of astrophysical simulations run by an international collaboration of scientists. The aim was to study the processes of galaxy formation and evolution in the universe with a comprehensive physical model. Early results were described in a number of publications following widespread press coverage. The project publicly released all data produced by the simulations in April, 2015. Key developers of the Illustris simulation have been Volker Springel and Mark Vogelsberger. The Illustris simulation framework and galaxy formation model has been used for a wide range of spin-off projects, starting with Auriga and IllustrisTNG followed by Thesan (2021), MillenniumTNG (2022) and TNG-Cluster.

Tom Quinn is a professor in the Department of Astronomy at the University of Washington (UW) in Seattle. He is the leader of the N-Body Shop, a faculty member of the astrobiology program at UW, and an affiliate member at the eScience Institute. He assisted in generating the cosmological simulation code called ChaNGA.

Ue-Li Pen is a Canadian astrophysicist, cosmologist, and computational physicist.

In cosmology, Gurzadyan-Savvidy (GS) relaxation is a theory developed by Vahe Gurzadyan and George Savvidy to explain the relaxation over time of the dynamics of N-body gravitating systems such as star clusters and galaxies. Stellar systems observed in the Universe – globular clusters and elliptical galaxies – reveal their relaxed state reflected in the high degree of regularity of some of their physical characteristics such as surface luminosity, velocity dispersion, geometric shapes, etc. The basic mechanism of relaxation of stellar systems has been considered the 2-body encounters, to lead to the observed fine-grained equilibrium. The coarse-grained phase of evolution of gravitating systems is described by violent relaxation developed by Donald Lynden-Bell. The 2-body mechanism of relaxation is known in plasma physics. The difficulties with description of collective effects in N-body gravitating systems arise due to the long-range character of gravitational interaction, as distinct of plasma where due to two different signs of charges the Debye screening takes place. The 2-body relaxation mechanism e.g. for elliptical galaxies predicts around years i.e. time scales exceeding the age of the Universe. The problem of relaxation and evolution of stellar systems and the role of collective effects are studied by various techniques, see. Among the efficient methods of study of N-body gravitating systems are the numerical simulations, particularly, Sverre Aarseth's N-body codes are widely used.

References

  1. ↑ "SciDAC Astrophysics Consortium". Retrieved 8 March 2012.
  2. ↑ AstroSim.net Archived 3 January 2012 at the Wayback Machine . Retrieved 8 March 2012.
  3. ↑ Breakthrough study confirms cause of short gamma-ray bursts. Astronomy.com website, 8 April 2011. Retrieved 20 November 2012.
  4. ↑ For example, see the article Cosmic Vibrations from Neutron Stars. Retrieved 21 March 2012.
  5. ↑ GALMER: GALaxy MERgers in the Virtual Observatory [ permanent dead link ] : News release. Retrieved 20 March 2012. Project Home page. Retrieved 20 Mar 2012.
  6. ↑ NASA Achieves Breakthrough In Black Hole Simulation; dated 18 April 2006. Recovered 18 March 2012.
  7. ↑ Lucio Mayer. Foreword: Advanced Science Letters (ASL), Special Issue on Computational Astrophysics.
  8. ↑ Hamada T., Nitadori K. (2010) 190 TFlops astrophysical N-body simulation on a cluster of GPUs. In Proceedings of the 2010 ACM/IEEE International Conference for High Performance Computing, Networking, Storage and Analysis (SC '10). IEEE Computer Society, Washington, DC, USA, 1-9. doi : 10.1109/SC.2010.1
  9. ↑ MODEST(MOdeling DEnse STellar systems) home page.. Retrieved 5 April 2012.
  10. ↑ NBodyLab.. Retrieved 5 April 2012.
  11. ↑ "Welcome to Starlab".
  12. ↑ Tom Theuns, Aidan Chalk, Matthieu Schaller, Pedro Gonnet: "SWIFT: task-based hydrodynamics and gravity for cosmological simulations"
  13. ↑ The RAMSES code
  14. ↑ Brian W. O'Shea, Greg Bryan, James Bordner, Michael L. Norman, Tom Abel, Robert Harkness, Alexei Kritsuk: "Introducing Enzo, an AMR Cosmology Application". Eds. T. Plewa, T. Linde & V. G. Weirs, Springer Lecture Notes in Computational Science and Engineering, 2004. arXiv:astro-ph/0403044 (Retrieved 20 Nov 2012);
    Project pages at:
  15. ↑ The Flash Center for Computational Science.. Retrieved 3 June 2012.
  16. ↑ Kravtsov, A.V., Klypin, A.A., Khokhlov, A.M., "ART: a new high resolution N-body code for cosmological simulations", ApJS, 111, 73, (1997)
  17. ↑ AMUSE(Astrophysical Multipurpose Software Environment)
  18. ↑ Portegies Zwart et al., "A multiphysics and multiscale software environment for modeling astrophysical systems", NewA, 14, 369, (2009)

Further reading

Beginner/intermediate level:

Advanced/graduate level:

Journals (Open Access):

This page is based on this Wikipedia article
Text is available under the CC BY-SA 4.0 license; additional terms may apply.
Images, videos and audio are available under their respective licenses.