On the dynamics of tidal streams in the Milky Way galaxy
  We present a brief history of Galactic astrophysics, and explain the origin
of halo substructure in the Galaxy. We motivate our study of tidal streams by
highlighting the tight constraints that analysis of the trajectories of tidal
streams can place on the form of the Galactic potential.
  We address the reconstruction of orbits from observations of tidal streams.
We upgrade the scheme reported by Binney (2008) and Jin & Lynden-Bell (2007),
which reconstructs orbits from streams using radial-velocity measurements, to
allow it to work with erroneous input data. The upgraded algorithm can correct
for both statistical error on observations, and systematic error due to streams
not delineating individual orbits, and given high-quality but realistic input
data, it can diagnose the potential with considerable accuracy.
  We complement the work of Binney (2008) by deriving a new algorithm, which
reconstructs orbits from streams using proper-motion data rather than radial
velocities. We show that the new algorithm has a similar potency for diagnosing
the Galactic potential.
  We explore the concept of Galactic parallax, which arises in connection with
our proper-motion study. Galactic parallax allows trigonometric distance
calculation to stars at 40 times the range of conventional parallax, although
its applicability is limited to only those stars in tidal streams.
  We examine from first principles the mechanics of tidal stream formation and
propagation. We find that the mechanics of tidal streams has a natural
expression in terms of action-angle variables. We find that tidal streams in
realistic galaxy potentials will generally not delineate orbits, and that
attempting to constrain the Galactic potential by assuming that they do can
lead to large systematic error. We show that we can accurately predict the
real-space trajectories of streams, even when they differ significantly from
orbits.
