We present initial results from the "Ponos" zoom-in numerical simulations of
dark matter substructures in massive ellipticals. Two very highly resolved dark
matter halos with Mvirβ=1.2Γ1013Mββ and Mvirβ=6.5Γ1012Mββ and different ("violent" vs. "quiescent")
assembly histories have been simulated down to z=0 in a ΞCDM
cosmology with a total of 921,651,914 and 408,377,544 particles, respectively.
Within the virial radius, the total mass fraction in self-bound Msubβ>106Mββ subhalos at the present epoch is 15% for the violent
host and 16.5% for the quiescent one. At z=0.7, these fractions increase to
19 and 33%, respectively, as more recently accreted satellites are less prone
to tidal destruction. In projection, the average fraction of surface mass
density in substructure at a distance of R/Rvirβ=0.02 (βΌ5β10 kpc)
from the two halo centers ranges from 0.6% to β³2%, significantly
higher than measured in simulations of Milky Way-sized halos. The contribution
of subhalos with Msubβ<109Mββ to the projected mass
fraction is between one fifth and one third of the total, with the smallest
share found in the quiescent host. We assess the impact of baryonic effects via
twin, lower-resolution hydrodynamical simulations that include
metallicity-dependent gas cooling, star formation, and a
delayed-radiative-cooling scheme for supernova feedback. Baryonic contraction
produces a super-isothermal total density profile and increases the number of
massive subhalos in the inner regions of the main host. The host density
profiles and projected subhalo mass fractions appear to be broadly consistent
with observations of gravitational lenses.Comment: 14 pages, 15 figures, accepted for publication in ApJ after minor
revisions, note the new Fig.