The Illustris project is an ongoing series of astrophysical

simulation A simulation is an imitative representation of a process or system that could exist in the real world. In this broad sense, simulation can often be used interchangeably with model. Sometimes a clear distinction between the two terms is made, in ...

s run by an international collaboration of scientists. The aim is to study the processes of

galaxy formation and evolution In cosmology, 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 process ...

in the

universe The universe is all of space and time and their contents. It comprises all of existence, any fundamental interaction, physical process and physical constant, and therefore all forms of matter and energy, and the structures they form, from s ...

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 Volker Springel is a German astrophysicist. He is Director of Computational Astrophysics at the Max Planck Institute for Astrophysics in Garching. Springel earned a degree in Physics from the University of Tübingen in 1996 and completed his Ph ...

(Max-Planck-Institut für Astrophysik) and Mark Vogelsberger (Massachusetts Institute of Technology). The Illustris simulation framework and galaxy formation model has been used for a wide range of spin-off projects, starting wit
Auriga
an
IllustrisTNG
(both 2017) followed b
Thesan
(2021)
MillenniumTNG
(2022) an
TNG-Cluster
(2023).

Illustris simulation

Overview

The original ''Illustris project'' was carried out by Mark Vogelsberger and collaborators as the first large-scale galaxy formation application of Volker Springel's novel Arepo code. The ''Illustris project'' included large-scale

cosmological Cosmology () is a branch of physics and metaphysics dealing with the nature of the universe, the cosmos. The term ''cosmology'' was first used in English in 1656 in Thomas Blount's ''Glossographia'', with the meaning of "a speaking of the wo ...

simulations A simulation is an imitative representation of a process or system that could exist in the real world. In this broad sense, simulation can often be used interchangeably with model. Sometimes a clear distinction between the two terms is made, in ...

of the evolution of the universe, spanning initial conditions of the

Big Bang The Big Bang is a physical theory that describes how the universe expanded from an initial state of high density and temperature. Various cosmological models based on the Big Bang concept explain a broad range of phenomena, including th ...

, to the present day, 13.8 billion years later. Modeling, based on the most precise data and calculations currently available, are compared to actual findings of the

observable universe The observable universe is a Ball (mathematics), spherical region of the universe consisting of all matter that can be observation, observed from Earth; the electromagnetic radiation from these astronomical object, objects has had time to reach t ...

in order to better understand the nature of the

, including

galaxy formation In cosmology, the study of galaxy formation and evolution is concerned with the processes that formed a Homogeneity and heterogeneity, heterogeneous universe from a Big Bang, homogeneous beginning, the formation of the first galaxies, the way ga ...

dark matter In astronomy, dark matter is an invisible and hypothetical form of matter that does not interact with light or other electromagnetic radiation. Dark matter is implied by gravity, gravitational effects that cannot be explained by general relat ...

and

dark energy In physical cosmology and astronomy, dark energy is a proposed form of energy that affects the universe on the largest scales. Its primary effect is to drive the accelerating expansion of the universe. It also slows the rate of structure format ...

. The simulation included many physical processes which are thought to be critical for galaxy formation. These include the formation of stars and the subsequent "feedback" due to supernova explosions, as well as the formation of super-massive black holes, their consumption of nearby gas, and their multiple modes of energetic feedback. Images, videos, and other data visualizations for public distribution are available a
official media page

Computational aspects

The main ''Illustris'' simulation was run on the Curie supercomputer at CEA (France) and the SuperMUC supercomputer at the Leibniz Computing Centre (Germany). A total of 19 million CPU hours was required, using 8,192 CPU cores. The peak memory usage was approximately 25 TB of RAM. A total of 136 snapshots were saved over the course of the simulation, totaling over 230 TB cumulative data volume. A code called "Arepo" was used to run the Illustris simulations. It was written by Volker Springel, the same author as the

GADGET A gadget is a machine, mechanical device or any ingenious article. Gadgets are sometimes referred to as ''wikt:gizmo, gizmos''. History The etymology of the word is disputed. The word first appears as reference to an 18th-century tool in Glass ...

code. The name is derived from the

Sator Square The Sator Square (or Rotas-Sator Square or Templar Magic Square) is a two-dimensional acrostic class of word square containing a five-word Latin palindrome. The earliest squares were found at Roman-era sites, all in ROTAS-form (where the top l ...

. This code solves the coupled equations of

gravity In physics, gravity (), also known as gravitation or a gravitational interaction, is a fundamental interaction, a mutual attraction between all massive particles. On Earth, gravity takes a slightly different meaning: the observed force b ...

and

hydrodynamics In physics, physical chemistry and engineering, fluid dynamics is a subdiscipline of fluid mechanics that describes the flow of fluids – liquids and gases. It has several subdisciplines, including (the study of air and other gases in ...

using a

discretization In applied mathematics, discretization is the process of transferring continuous functions, models, variables, and equations into discrete counterparts. This process is usually carried out as a first step toward making them suitable for numeri ...

of space based on a moving

Voronoi tessellation Voronoi or Voronoy is a Slavic masculine surname; its feminine counterpart is Voronaya. It may refer to *Georgy Voronoy (1868–1908), Russian and Ukrainian mathematician **Voronoi diagram **Weighted Voronoi diagram ** Voronoi deformation density ** ...

. It is optimized for running on large, distributed memory supercomputers using an

MPI MPI or Mpi may refer to: Science and technology Biology and medicine * Magnetic particle imaging, a tomographic technique * Myocardial perfusion imaging, a medical procedure that illustrates heart function * Mannose phosphate isomerase, an enzyme ...

approach.

Public data release

In April, 2015 (eleven months after the first papers were published) the project team publicly released all data products from all simulations. All original data files can be directly downloaded through th
data release webpage
This includes group catalogs of individual halos and subhalos, merger trees tracking these objects through time, full snapshot particle data at 135 distinct time points, and various supplementary data catalogs. In addition to direct data download, a web-based API allows for many common search and

data extraction Data extraction is the act or process of retrieving data out of (usually unstructured or poorly structured) data sources for further data processing or data storage (data migration). The import into the intermediate extracting system is thus usual ...

tasks to be completed without needing access to the full data sets.

German postage stamp

In December 2018, the Illustris simulation was recognized by

Deutsche Post (, ) is a brand of the DHL Group (listed as ), used for its domestic mail services in Germany. The services offered under the brand are those of a traditional mail service, making the brand the successor of the former state-owned mail monopoly ...

through a special series stamp.

Illustris Spin-Off Projects

The Illustris simulation framework has been used by a wide range of spin-off projects that focus on specific scientific questions. IllustrisTNG: Th
IllustrisTNG project
"the next generation" follow up to the original Illustris simulation, was first presented in July, 2017. A team of scientists from Germany and the U.S. led by Prof. Volker Springel. First, a new physical model was developed, which among other features included

Magnetohydrodynamics In physics and engineering, magnetohydrodynamics (MHD; also called magneto-fluid dynamics or hydromagnetics) is a model of electrically conducting fluids that treats all interpenetrating particle species together as a single Continuum ...

planned three simulations, which used different volumes at different resolutions. The intermediate simulation (TNG100) was equivalent to the original Illustris simulation. Unlike Illustris, it was run on the Hazel Hen machine at the High Performance Computing Center, Stuttgart in Germany. Up to 25,000 computer cores were employed. In December 2018 the simulation data from IllustrisTNG was released publicly. The data service includes a JupyterLab interface. Auriga: Th
Auriga
project consists of high-resolution zoom simulations of Milky Way-like dark matter halos to understand the formation of our Milky Way galaxy. Thesan: Th
Thesan project
is a radiative-transfer version of IllustrisTNG to explore the epoch of reionization. MillenniumTNG: Th
MillenniumTNG
employs the IllustrisTNG galaxy formation model in a larger cosmological volume to explore the massive end of the halo mass function for detailed cosmological probe forecasts. TNG-Cluster: A suite of high-resolution zoom-in simulations of galaxy clusters.

Gallery

References

External links

*
Press release
- Center for Astrophysics Harvard & Smithsonian (7 May 2014). *
Illustris-Project
(6 May 2014). * -

NASA The National Aeronautics and Space Administration (NASA ) is an independent agencies of the United States government, independent agency of the federal government of the United States, US federal government responsible for the United States ...

(14 July 2014) * - article containing a comparison table of different simulation projects {{Portal bar, Astronomy, Physics, Space Astrophysics Cosmological simulation Physical cosmology