On the Orbits of Infalling Satellite Halos
  The orbital properties of infalling satellite halos set the initial
conditions which control the subsequent evolution of subhalos and the galaxies
that they host, with implications for mass stripping, star formation quenching,
and merging. Using a high-resolution, cosmological N-body simulation, I examine
the orbital parameters of satellite halos as they merge with larger host halos,
focusing primarily on orbital circularity and pericenter. I explore in detail
how these orbital parameters depend on mass and redshift. Satellite orbits
become more radial and plunge deeper into their host halo at higher host halo
mass, but they do not significantly depend on satellite halo mass.
Additionally, satellite orbits become more radial and plunge deeper into their
host halos at higher redshift. I also examine satellite velocities, finding
that most satellites infall with less specific angular momentum than the host
halo virial value, but that satellites are `hotter' than the host virial
velocity. I discuss the implications of these results to the processes of
galaxy formation and evolution, and I provide fitting formulas to the mass and
redshift dependence of satellite orbital circularity and pericenter.
