Orientation of the disk galaxies in the Coma cluster

The orientations of the spin vectors of 128 disk galaxies (66 S0 galaxies, 62 S and Irr galaxies) in the Coma cluster have been statistically studied. With respect to the expected isotropic distribution, the distribution of the spin vectors in the Coma cluster is shown to be anisotropic, in the sense that S0 galaxies tend to have their spin vectors parallel to the cluster plane, while the spin vectors of S and Irr galaxies tend to be parallel or perpendicular to the cluster plane. The excess orientation of the projection on the cluster plane of the spin vectors of all disk galaxies are around directions which deviate from the direction pointing to the cluster center by an angle of 30 degrees. Additionally, the projection on the cluster plane of the spin vectors of S and Irr galaxies also tend to point towards the cluster center. The results are discussed in the context of theories of the formation of galaxies and clusters of galaxies.