The Millennium simulation is an extremely large N-body simulation carried out by the Virgo Consortium. It simulates the gravitational evolution of a section of universe 500Mpc/h across using approximately ten billion particles. These pages are intended for people working with the data and provide some information about how to access the raw particle data, the FoF and SubFind groups, and the Durham version of the halo merger trees.
Galaxy catalogues generated using the models described by Bower et al (2006) and De Lucia & Blaizot (2006) are now available online in a searchable SQL database. Mirrors of this database exist in Durham and Garching.
There are some Fortran 90 modules to simplify reading the Millennium simulation particle data and FoF/SubFind group files. These should work with other L-Gadget2 simulations too. The code, along with some documentation and example programs, is available here.
For help reading the data in C or IDL, see Volker's Millennium web page.
This page explains the organisation and format of the Durham version of the halo merger trees derived from the Millennium simulation. There are also some code fragments showing how to read the data in Fortran.