The Three Rings
Narya, Nenya and Vilya are the Three Rings. These three (paired-and-fixed, Angulo & Pontzen, 2010 ) simulations are the backbone of the bacco project. Each of them represents a cube of the universe \(1440 h^{-1} \mathrm{Mpc}\) wide, containing \(4320^3\) cold matter particles.
The BACCO simulations were carried out in the Summer of 2019 at Marenostrum-IV at the Barcelona Supercomputing Center (BSC) in Spain. We employed an updated version of the L-Gadget3 N-body code in a hybrid distributed/shared memory setup with 8192 cores using 4096 MPI tasks. The run time was 7.2 million CPU hours, equivalent of 35 days of wall-clock time. The total storage required for all data products is about 80 TB.
Each simulation assumes a different cosmology, and the three cosmologies have been carefully chosen: starting from these three points in parameter space, we can create scaled simulations in any other cosmology (including those with massive neutrinos, see Zennaro et al, 2019), keeping the error to a minimum. So it is thanks to the Three Rings that we are able to use one (three) simulation to fit them all!
| Narya | Nenya | Vilya | |
|---|---|---|---|
| \( \Omega_{\rm cdm} \) | \( 0.31 \) | \( 0.265 \) | \( 0.21 \) |
| \( \Omega_{\rm b} \) | \( 0.05 \) | \( 0.05 \) | \( 0.06 \) |
| \( h \) | \( 0.7 \) | \( 0.6 \) | \( 0.65 \) |
| \( n_{\rm s} \) | \( 1.01 \) | \( 1.01 \) | \( 0.92 \) |
| \( 10^9 A_{\rm s} \) | \( 1.8444 \) | \( 3.1802 \) | \( 4.1220 \) |
| \( \sigma_8 \) | \( 0.9 \) | \( 0.9 \) | \( 0.9 \) |
| \( M_\nu [\mathrm{eV}] \) | \( 0 \) | \( 0 \) | \( 0 \) |
| \( w_0 \) | \( -1 \) | \( -1 \) | \( -1 \) |
| \( w_a \) | \( 0 \) | \( 0 \) | \( 0 \) |