The Cosmogrid Simulation: Statistical Properties of Small Dark Matter
  Halos
  We present the results of the "Cosmogrid" cosmological N-body simulation
suites based on the concordance LCDM model. The Cosmogrid simulation was
performed in a 30Mpc box with 2048^3 particles. The mass of each particle is
1.28x10^5 Msun, which is sufficient to resolve ultra-faint dwarfs. We found
that the halo mass function shows good agreement with the Sheth & Tormen
fitting function down to ~10^7 Msun. We have analyzed the spherically averaged
density profiles of the three most massive halos which are of galaxy group size
and contain at least 170 million particles. The slopes of these density
profiles become shallower than -1 at the inner most radius. We also find a
clear correlation of halo concentration with mass. The mass dependence of the
concentration parameter cannot be expressed by a single power law, however a
simple model based on the Press-Schechter theory proposed by Navarro et al.
gives reasonable agreement with this dependence. The spin parameter does not
show a correlation with the halo mass. The probability distribution functions
for both concentration and spin are well fitted by the log-normal distribution
for halos with the masses larger than ~10^8 Msun. The subhalo abundance depends
on the halo mass. Galaxy-sized halos have 50% more subhalos than ~10^{11} Msun
halos have.
