Velocity dispersion measurements of dwarf galaxies in the Coma cluster -
  implications for the structure of the fundamental plane
  We present intermediate-resolution spectroscopic data for a set of dwarf and
giant galaxies in the Coma Cluster, with -20.6 < M_R < -15.7. The photometric
and kinematic properties of the brighter galaxies can be cast in terms of
parameters which present little scatter with respect to a set of scaling
relations known as the Fundamental Plane. To determine the form of these
fundamental scaling relations at lower luminosities, we have measured velocity
dispersions for a sample comprising 69 galaxies on the border of the dwarf and
giant regime. Combining these data with our photometric survey, we find a tight
correlation of luminosity and velocity dispersion, L \propto \sigma^{2.0},
substantially flatter than the Faber-Jackson relation characterising giant
elliptical galaxies. In addition, the variation of mass-to-light ratio with
velocity dispersion is quite weak in our dwarf sample: M/L \propto
\sigma^{0.2}. Our overall results are consistent with theoretical models
invoking large-scale mass removal and subsequent structural readjustment, e.g.,
as a result of galactic winds.
