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# Some basic details about the Millennium-II simulation:

• Cosmological parameters are identical to those used in both the Millennium run and the Aquarius simulations:
$\Omega_m=0.25, \; \Omega_{\Lambda}=0.75, \; \Omega_b=0.045, \; h=0.73, \; \sigma_8=0.9,\; n=1\,.$
• The initial conditions use the same phases and amplitudes for the Fourier modes as the run from which the Aquarius halos were selected
• 68 snapshots: 60 at identical redshifts as Millennium (to $z \approx 20$), continuing with same spacing scheme as Millennium out to $z \approx 31,\!$ with additional snapshots at $z=40,\!$ 80, and 127 (the initial redshift for the simulation)
• Performed with P-Gadget3 on 2048 cores of the MPG's IBM Power6 computer at the Rechenzentrum Garching (RZG)
• computational time: $\approx 1.4$ million hours
• up to 22,000 individual timesteps
• box size: $L=100 \; h^{-1}\, \mathrm{Mpc}$
• particle number: $\!2160^3$ = 10,077,696,000
• particle mass: $6.885 \times 10^6 \;h^{-1}\, M_{\odot}$
• force resolution: $\epsilon=1 \;h^{-1}\, \mathrm{kpc}$ (Plummer-equivalent softening)
• Largest FOF halo: 119 million particles (and over 35,000 subhalos)
• Approximately 12 million FOF halos at $z=0$, down from a maximum of over 15 million at $z=3$
• Over 60$\%$ of particles lie in resolvable FOF groups (20 particle limit, with $b=0.2$) at $z=0$
• Compared to the Millennium simulation, the Millennium-II run has $1/125^{\mathrm{th}}$ the volume but 125 times better mass resolution and 5 times better force resolution; the particle number and dynamic range $L / \epsilon = 10^5$ are the same for both runs.