The Dynamical Relationship Between the Bar and Spiral Patterns of NGC
  1365
  Theories that attempt to explain the dynamical relationship between bar and
spiral patterns in galactic disks make different predictions about the radial
profile of the pattern speed. These are tested for the H-alpha bar and spiral
patterns of NGC 1365. The radial profile of the pattern speed is measured by
fitting mathematical models that are based on the Tremaine-Weinberg method. The
results show convincing evidence for the bar rotating at a faster rate than the
spiral pattern, inconsistent with a global wave mode or a manifold. There is
evidence for mode coupling of the bar and spiral patterns at the overlap of
corotation and inner Lindblad resonances, but the evidence is unreliable and
inconsistent. The results are the most consistent with the bar and spiral
patterns being dynamically distinct features. The pattern speed of the bar
begins near an ILR and ends near the corotation resonance. The radial profile
of the pattern speed beyond the bar most closely resembles what is expected for
coupled spiral modes and tidal interactions.
