Kinematic classification of non-interacting spiral galaxies
  Using neutral hydrogen (HI) rotation curves of 79 galaxies, culled from the
literature, as well as measured from HI data, we present a method for
classifying disk galaxies by their kinematics. In order to investigate
fundamental kinematic properties we concentrate on non-interacting spiral
galaxies. We employ a simple parameterized form for the rotation curve in order
to derive the three parameters: the maximum rotational velocity, the turnover
radius and a measure of the slope of the rotation curve beyond the turnover
radius. Our approach uses the statistical Hierarchical Clustering method to
guide our division of the resultant 3D distribution of galaxies into five
classes. Comparing the kinematic classes in this preliminary classification
scheme to a number of galaxy properties we find that our class containing
galaxies with the largest rotational velocities has a mean morphological type
of Sb/Sbc while the other classes tend to later types. Other trends also
generally agree with those described by previous researchers. In particular we
confirm correlations between increasing maximum rotational velocity and the
following observed properties: increasing brightness in B-band, increasing size
of the optical disk (D_25) and increasing star formation rate (as derived using
radio continuum data). Our analysis also suggests that lower velocities are
associated with a higher ratio of the HI mass over the dynamical mass.
Additionally, three galaxies exhibit a drop in rotational velocity amplitude of
>~ 20% after the turnover radius. However recent investigations suggest that
they have interacted with minor companions which is a common cause for
declining rotation curves. (Figures 12, 14, 16 and 17 are interactive in the
electronic pdf version of this paper.)
