All of the results and data products of the Illustris simulation project, as described in Nelson+ (2015), are made publicly available on this page. A number of tools for exploration and analysis are provided as a starting point.

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There are two fundamental ways you can engage with the Illustris data:

  • (i) you can download the raw data files and example scripts in order to work completely on your local system. Start with the Example Scripts tutorial.
  • (ii) you can use the online API to interact with specific objects of interest without needing to download any full datafiles. Start with the API tutorial.

These two approaches can be combined. For example, you may be forced to download the full z=0 group catalog in order to perform a complex search not supported by the API. After locally determining a sample of interesting galaxies, you could then extract their individual merger trees (and/or raw particle data) without needing to download the full simulation merger tree (or a full snapshot).


  • Background and Important Details - overview of the simulations, physical models, references, caveats and cautions, and suggestions for citation
  • Data Specifications - description of all fields in the snapshots, group catalogs, merger trees, and supplementary data sets
  • Example Scripts - getting-started guide and reference for the basic I/O examples provided for working with the raw data files (Python, IDL, Matlab)
  • Web-based API - getting-started guide, cookbook of examples, and reference for the web-based query interface (Python, IDL, Matlab)
  • Frequently Asked Questions - do check the FAQ first

Raw Data Downloads

There are three primary types of data for each simulation: snapshots, group catalogs, and merger trees. In addition, certain runs and/or snapshots may have additional data catalogs. Select a simulation to browse the available data files and get direct download links:

Simulation Name $L_{\rm box} [Mpc]$ $N_{\rm DM}$ $m_{\rm DM}$ $[M_\odot]$ $m_{\rm gas}$ $[M_\odot]$ $N_{\rm snap}$ $N_{\rm Subfind} (z=0)$ Snaps FoF Subfind SubLink LHaloTree
Illustris-1 $106.5$ $1820^3$ $6.3 \times 10^{6}$ $1.3 \times 10^{6}$ $134$ $4366546$
Illustris-1-Dark $106.5$ $1820^3$ $7.5 \times 10^{6}$ $0$ $136$ $4872374$
Illustris-2 $106.5$ $910^3$ $5.0 \times 10^{7}$ $1.0 \times 10^{7}$ $136$ $689785$
Illustris-2-Dark $106.5$ $910^3$ $6.0 \times 10^{7}$ $0$ $136$ $735751$
Illustris-3 $106.5$ $455^3$ $4.0 \times 10^{8}$ $8.1 \times 10^{7}$ $136$ $121209$
Illustris-3-Dark $106.5$ $455^3$ $4.8 \times 10^{8}$ $0$ $136$ $111992$

Currently showing 6 runs with 814 total snapshots and 250.2 TB total data volume,
including 1,259,309,875 FoF groups, 1,175,372,132 Subfind groups, and 2,765,286,583,516 particles.

Simulation Name Parent Sim $L_{\rm box} [Mpc]$ $N_{\rm DM} (z=0)$ $m_{\rm DM}$ $[M_\odot]$ $N_{\rm snap}$ Snaps FoF Subfind
Subboxes: Didn't find anything available for you (try logging in).

Subboxes: currently showing 0 runs with 0 total snapshots and 0 bytes total data volume, including 0 FoF groups, 0 Subfind groups, and 0 particles.

Simulation Name Description $m_{\rm DM}$ $[M_\odot]$ $N_{\rm snap}$
Other Runs: Didn't find anything else for you at the moment (if you were expecting to have access to additional data, contact us).

Other runs: currently showing 0 runs with 0 total snapshots and 0 bytes total data volume, including 0 FoF groups, 0 Subfind groups, and 0 particles.

Web-based Exploration

No need to write code to explore -- by drilling down on interesting objects within any of these browser-based tools you can: get properties, render and explore merger trees, extract particle data cutouts from the snapshots, and see available visualizations.

  • Group Catalog Search - query the subhalo catalog in the online database
  • Browsable API - the online API is also human-navigable in your web browser
  • The Explorer - deep zoom map interface (of a slice of Illustris-1 at z=0)
  • Galaxy Observatory - search and browse stellar images, currently restricted to Illustris-1 z=0 galaxies which have 'stellar mocks'

Community and Support

We welcome community involvement in this project. Have some (fast) python code that performs a specific analysis task on a galaxy, and want to add it to the API so that it can be run on-the-fly? Have some (slow, complex) code that you have developed on a single halo cutout, and would like us to run it on all halos and make the results available as a supplementary data product? Get in touch!

  • Discussion Forum - get help, includes a changelog of additions/updates
  • Bitbucket Repository - get involved directly by making a pull request/issue
  • Contact Us with inquiries for participation, collaboration, or comments in general