The MultiDark Database: Release of the Bolshoi and MultiDark Cosmological Simulations (1109.0003v2)

Abstract: We present the online MultiDark Database -- a Virtual Observatory-oriented, relational database for hosting various cosmological simulations. The data is accessible via an SQL (Structured Query Language) query interface, which also allows users to directly pose scientific questions, as shown in a number of examples in this paper. Further examples for the usage of the database are given in its extensive online documentation (www.multidark.org). The database is based on the same technology as the Millennium Database, a fact that will greatly facilitate the usage of both suites of cosmological simulations. The first release of the MultiDark Database hosts two 8.6 billion particle cosmological N-body simulations: the Bolshoi (250/h Mpc simulation box, 1/h kpc resolution) and MultiDark Run1 simulation (MDR1, or BigBolshoi, 1000/h Mpc simulation box, 7/h kpc resolution). The extraction methods for halos/subhalos from the raw simulation data, and how this data is structured in the database are explained in this paper. With the first data release, users get full access to halo/subhalo catalogs, various profiles of the halos at redshifts z=0-15, and raw dark matter data for one time-step of the Bolshoi and four time-steps of the MultiDark simulation. Later releases will also include galaxy mock catalogs and additional merging trees for both simulations as well as new large volume simulations with high resolution. This project is further proof of the viability to store and present complex data using relational database technology. We encourage other simulators to publish their results in a similar manner.

• The paper presents a robust database infrastructure that efficiently manages and queries high-resolution N-body simulation data via SQL.
• The paper details two simulations with 8.6 billion particles each, enabling precise studies of dark matter halos and cosmic structure formation.
• The paper provides comprehensive halo catalogues, merger trees, and raw particle data, offering vital tools for analyzing galaxy evolution.

Overview of the MultiDark Database: Bolshoi and MultiDark Cosmological Simulations

The paper "The MultiDark Database: Release of the Bolshoi and MultiDark Cosmological Simulations" outlines the creation and structuring of the MultiDark Database, a vital tool for astronomical research. The database's release includes two significant N-body cosmological simulations: Bolshoi and MultiDark Run1 (also known as BigBolshoi), each with 8.6 billion particles. These simulations provide crucial data for the paper of dark matter halos, structure formation, and galaxy clustering, offering researchers a sophisticated means of querying and analyzing extensive simulation outputs via SQL through a Virtual Observatory framework.

Key Components and Features

1. Cosmological and Numerical Parameters: Both simulations utilize cosmological parameters aligned with WMAP5 and WMAP7 data, differing slightly from the Millennium simulations. The Bolshoi simulation encompasses a 250 $h^{-1}$Mpc simulation box with 1 $h^{-1}$kpc resolution, while the MultiDark Run1 simulation covers a 1000 $h^{-1}$Mpc box with 7 $h^{-1}$kpc resolution. Precise control over these parameters allows for a rigorous exploration of large-scale cosmic structures.
2. Database Design and Access: The relational database model aids in the efficient management and retrieval of complex datasets, providing a structured environment through SQL queries. Utilizing technology similar to the Millennium Database, it facilitates a user-friendly interface for executing scientific questions. SQL's powerful query capabilities allow for server-side data filtering and analysis, critical for working with simulations that produce data on a multi-terabyte scale.
3. Halo and Subhalo Catalogs: Two primary methodologies are used to identify halos: the Bound Density Maximum (BDM) method and the Friends-of-Friends (FOF) algorithm. BDM catalogs distinguish between virial and 200 times critical density thresholds, while FOF employs multiple linking lengths to classify substructures. This setup is critical for investigating the intricacies of halo formation and interaction over cosmic time scales.
4. Raw Particle Data Access: A notable feature is the provision of complete raw simulation data for selected snapshots, allowing users direct interaction with particle information. This fosters thorough examination and secondary analysis, such as testing alternative halo-finding algorithms or calculating custom properties.
5. Merger and Substructure Trees: The database includes extensive merger trees for FOF halos and substructure delineations, cataloging hierarchical relationships that inform studies on galaxy evolution and formation histories. These trees are indispensable for tracing back the assembly histories of halos and modeling galaxy evolution through semi-analytic techniques.
6. Practical and Research Implications: The integration of such a robust database aids in large-scale survey preparation and interpretation, including SDSS-III/BOSS and DES. Furthermore, it provides a critical resource for theoretical model validation, offering a platform for cross-comparison of datasets from simulations conducted under different numerical schemes and with varied cosmological inputs.

Future Prospects

The paper outlines plans for future database upgrades, which include additional snapshots, galaxy mock catalogs, and new high-resolution simulations. These expansions will significantly enhance the database's utility, making it an ever more indispensable resource for upcoming cosmological studies and observational correlations.

By design, the MultiDark Database facilitates reproducible and transparent research within the cosmological community, encouraging the integration of simulation data into common research paradigms. The work reflects a decisive move towards large, accessible databases in astrophysics that maximize the scientific return from complex simulations and enhance collaborative opportunities across the field.