  We use high-resolution numerical simulations to study the physical properties
of subhalos when they merge into their host halos. An improved algorithm is
used to identify the subhalos. We then examine their spatial and velocity
distributions in spherical and triaxial halo models. We find that the accretion
of satellites preferentially occurs along the major axis and perpendicular to
the spin axis of the host halo. Furthermore, the massive subhalos show a
stronger preference to be accreted along the major axis of the host halo than
the low-mass ones. Approximate fitting formulae are provided for the physical
properties of subhalos. Combined with analytical and semi-analytic techniques,
these empirical formulae provide a useful basis for studying the subsequent
evolution of subhalos and satellite galaxies in their hosts. Future studies
should however account for satellites that may not be undergoing the first
infall in their evolution.
