Galactic Orbits of Selected Companions of the Milky Way
  High-accuracy absolute proper motions, radial velocities, and distances have
now been measured for a number of dwarf-galaxy companions of the Milky Way,
making it possible to study their 3D dynamics. Galactic orbits for 11 such
galaxies (Fornax, Sagittarius, Ursa Minor, LMC, SMC, Sculptor, Sextans, Carina,
Draco, Leo I, Leo II) have been derived using two previously refined models for
the Galactic potential with the Navarro-Frenk-White and Allen-Santill'an
expressions for the potential of the dark-matter halo, and two different masses
for the Galaxy within 200 kpc - 0.75x10^12 Mo and 1.45x10^12 Mo. The character
of the orbits of most of these galaxies indicates that they are tightly
gravitationally bound to the Milky Way, even with the lower-mass model for the
gravitational potential. One exception is the most distant galaxy in the list,
Leo I, whose orbit demonstrates that it is only weakly gravitationally bound,
even using the higher-mass model of the gravitational potential.
