[Paper Review] Public Release of N-body simulation and related data by the Virgo consortium

Carlos S. Frenk, J. M. Colberg+11 more|arXiv (Cornell University)|Jul 25, 2000

Galaxies: Formation, Evolution, Phenomena30 references10 citations

TL;DR

This paper presents the public release of high-resolution N-body simulations and related datasets from the Virgo Consortium, including Hubble-volume simulations with 1 billion particles, 256³-particle cosmological models, and galaxy formation data from the GIF project. The data enable large-scale studies of dark matter clustering, halo properties, and galaxy formation, with key results on mass functions, weak lensing, and cosmic structure statistics across multiple cosmological models.

ABSTRACT

We are making available on the WWW a selection of the archived data from N-body simulations carried out by the Virgo consortium and related groups. This currently includes: (i) time-slice, lightcone and cluster data from the two $10^9$-particle Hubble volume simulations described by Evrard 1998; (ii) time-slice data from simulations of 4 different cold dark matter cosmological models with $256^3$ particles analysed by Jenkins et al 1998; (iii) Dark halo catalogs, merger trees and galaxy catalogs from the GIF project described by Kauffmann et al 1999. Basic software is supplied to read the data. The data can be accessed from: http://www.mpa-garching.mpg.de/Virgo/data_download.html

Motivation & Objective

• To provide open access to high-resolution cosmological N-body simulations and derived datasets for the broader astrophysics community.
• To enable detailed studies of dark matter clustering, halo formation, and galaxy evolution across diverse cosmological models.
• To support observational cosmology by providing mock data for testing power spectrum estimates, weak lensing, and cluster statistics.
• To facilitate validation of analytic models of halo bias, mass function, and large-scale structure using high-dynamic-range simulations.
• To establish a centralized, sustainable data repository with software tools for accessing and analyzing simulation outputs.

Proposed method

• Conducting large-scale N-body simulations on parallel supercomputers using particle-mesh and tree-based algorithms to model cold dark matter evolution.
• Simulating four cosmological models: flat ΛCDM, open OCDM, standard CDM (SCDM), and τCDM, with varying Ω₀, Λ₀, and σ₈.
• Producing time-slice outputs, light-cone surveys, and cluster catalogs from the Hubble-volume simulations (10⁹ particles, 2000–3000 h⁻¹ Mpc boxes).
• Generating high-resolution 256³-particle simulations to study halo mass functions and clustering statistics with high dynamic range.
• Creating galaxy catalogs, merger trees, and dark halo catalogs via semi-analytic modeling in the GIF project, incorporating baryonic physics and feedback.
• Hosting data and software tools at a central web repository (http://www.mpa-garching.mpg.de/Virgo/data_download.html) for public download or tape request.

Experimental results

Research questions

• RQ1 How do clustering statistics such as the two-point correlation function and counts-in-cells distribution behave in large-scale N-body simulations?
• RQ2 What are the properties of dark matter halos, including their mass function, velocity dispersion, and large-scale environment, across different cosmological models?
• RQ3 How do weak lensing shear fields and strong lensing cross-sections in simulated clusters compare to observational expectations?
• RQ4 To what extent can semi-analytic galaxy formation models reproduce observed galaxy clustering and bias in simulated dark matter distributions?
• RQ5 How do mock galaxy catalogs from simulations help quantify uncertainties in observational power spectrum estimates from finite surveys?

Key findings

• The Hubble-volume simulations with 1 billion particles span 2000–3000 h⁻¹ Mpc comoving volumes, enabling unprecedented statistical accuracy in clustering diagnostics.
• The simulations reveal that cluster-rich regions contain tens of thousands of massive halos, with Coma-like clusters resolved in 500 particles within an Abell radius.
• The mass function of dark matter halos was measured over more than four orders of magnitude in mass, supporting the validity of analytic models like Sheth-Tormen.
• Mock galaxy catalogs from the GIF project show that semi-analytic models reproduce observed galaxy clustering and higher-order correlations, as validated against the PSCz survey.
• Light-cone outputs from the Hubble volume simulations allow realistic modeling of survey effects, including sampling uncertainties in power spectrum estimation.
• The data have been used in over 20 refereed publications by 2000, including studies on weak lensing, Sunyaev-Zel’dovich effects, and halo topology, demonstrating broad scientific impact.