  A prediction of the standard LCDM cosmology is that dark matter (DM) halos
are teeming with numerous self-bound substructure, or subhalos. The precise
properties of these subhalos represent important probes of the underlying
cosmological model. We use data from Via Lactea II and ELVIS N-body simulations
to learn about the structure of subhalos with masses 1e6 - 1e11 Msun/h. Thanks
to a superb subhalo statistics, we study subhalo properties as a function of
distance to host halo center and subhalo mass, and provide a set of fits that
accurately describe the subhalo structure. We also investigate the role of
subhalos on the search for DM annihilation. Previous work has shown that
subhalos are expected to boost the DM signal of their host halos significantly.
Yet, these works traditionally assumed that subhalos exhibit similar structural
properties than those of field halos, while it is known that subhalos are more
concentrated. Building upon our N-body data analysis, we refine the
substructure boost model of Sanchez-Conde & Prada (2014), and find boosts that
are a factor 2-3 higher. We further refine the model to include unavoidable
tidal stripping effects on the subhalo population. For field halos, this
introduces a moderate 20-30% suppression. Yet, for subhalos like those hosting
dwarf galaxy satellites, tidal stripping plays a critical role, the boost being
at the level of a few tens of percent at most. We provide a parametrization of
the boost for field halos that can be safely applied over a wide halo mass
range.
