Halo and Galaxy Formation Histories from the Millennium Simulation: Public release of a VO-oriented and SQL-queryable database for studying the evolution of galaxies in the LambdaCDM cosmogony

The Millennium Run is the largest simulation of the formation of structure within the $\Lambda$CDM cosmogony so far carried out. It uses $10^{10}$ particles to follow the dark matter distribution in a cubic region 500$h^{-1}$Mpc on a side, and has a spatial resolution of 5 $h^{-1}$kpc. Application of simplified modelling techniques to the stored output of this calculation allows the formation and evolution of the $\sim 10^7$ galaxies more luminous than the Small Magellanic Cloud to be simulated for a variety of assumptions about the detailed physics involved. As part of the activities of the German Astrophysical Virtual Observatory we have used a relational database to store the detailed assembly histories both of all the haloes and subhaloes resolved by the simulation, and of all the galaxies that form within these structures for two independent models of the galaxy formation physics. We have created web applications that allow users to query these databases remotely using the standard Structured Query Language (SQL). This allows easy access to all properties of the galaxies and halos, as well as to the spatial and temporal relations between them and their environment. Information is output in table format compatible with standard Virtual Observatory tools and protocols. With this announcement we are making these structures fully accessible to all users. Interested scientists can learn SQL, gain familiarity with the database design and test queries on a small, openly accessible version of the Millennium Run (with volume 1/512 that of the full simulation). They can then request accounts to run similar queries on the databases for the full simulations.