Quantifying galactic morphological transformations in the cluster
  environment
  We study the effects of the cluster environment on galactic morphology by
defining a dimensionless angular momentum parameter $\lambda_{d}$, to obtain a
quantitative and objective measure of galaxy type. The use of this physical
parameter allows us to take the study of morphological transformations in
clusters beyond the measurements of merely qualitative parameters, e.g. S/E
ratios, to a more physical footing. To this end, we employ an extensive Sloan
Digital Sky Survey sample (Data Release 7), with galaxies associated with Abell
galaxy clusters. The sample contains 121 relaxed Abell clusters and over 51,000
individual galaxies, which guarantees a thorough statistical coverage over a
wide range of physical parameters. We find that the median $\lambda_{d}$ value
tends to decrease as we approach the cluster center, with different dependences
according to the mass of the galaxies and the hosting cluster; low and
intermediate mass galaxies showing a strong dependence, while massive galaxies
seems to show, at all radii, low $\lambda_{d}$ values. By analysing trends in
$\lambda_{d}$ as functions of the nearest neighbour environment, clustercentric
radius and velocity dispersion of clusters, we can identify clearly the leading
physical processes at work. We find that in massive clusters ($\sigma>700$
km/s), the interaction with the cluster central region dominates, whilst in
smaller clusters galaxy-galaxy interactions are chiefly responsible for driving
galactic morphological transformations.
