Galaxy Morphology
  Galaxy morphology has many structures that are suggestive of various
processes or stages of secular evolution. Internal perturbations such as bars
can drive secular evolution through gravity torques that move gas into the
central regions and build up a flattened, disk-like central bulge, or which may
convert an open spiral pseudoring into a more closed ring. Interaction between
individual components of a galaxy, such as between a bar and a dark halo, a bar
and a central mass concentration, or between a perturbation and the basic state
of a stellar disk, can also drive secular transformations. In this series of
lectures, I review many aspects of galaxy morphology with a view to delineating
some of the possible evolutionary pathways between different galaxy types.
