S-tree Analysis of the Substructure of the Coma Cluster

The S-tree method is used to estimate the redshift of the core of Coma cluster - $cz = 6953$ km s$^{-1}$ and dispersion $\sigma=949$ km s$^{-1}$. The existence of three subgroups of galaxies is revealed, one of them is associated with the cD galaxy NGC 4874, another - with NGC 4889. It is argued that these subgroups are 'galaxy associations', i.e. galactic dynamical entities moving through the main cluster. The non-stationarity of the dynamical processes ongoing in the Coma core is concluded.