Multivariate analysis of the globular clusters in M87
  An objective classification of 147 globular clusters in the inner region of
the giant elliptical galaxy M87 is carried out with the help of two methods of
multivariate analysis. First independent component analysis is used to
determine a set of independent variables that are linear combinations of
various observed parameters (mostly Lick indices) of the globular clusters.
Next K-means cluster analysis is applied on the independent components, to find
the optimum number of homogeneous groups having an underlying structure. The
properties of the four groups of globular clusters thus uncovered are used to
explain the formation mechanism of the host galaxy. It is suggested that M87
formed in two successive phases. First a monolithic collapse, which gave rise
to an inner group of metal-rich clusters with little systematic rotation and an
outer group of metal-poor clusters in eccentric orbits. In a second phase, the
galaxy accreted low-mass satellites in a dissipationless fashion, from the gas
of which the two other groups of globular clusters formed. Evidence is given
{\bf for a blue stellar population in the more metal rich clusters, which we
interpret by Helium enrichment.} Finally, it is found that the clusters of M87
differ in some of their chemical properties (NaD, TiO1, light element
abundances) from globular clusters in our Galaxy and M31.
