Spatial orientation of galaxies in the core of the Shapley concentration – the cluster Abell 3558
Institut für Astrophysik, Universität Innsbruck, Technikerstraße 25, 6020 Innsbruck, Austria e-mail: [binil.aryal;walter.saurer]@uibk.ac.at
2 Central Department of Physics, Tribhuvan University, Kirtipur, Kathmandu, Nepal e-mail: email@example.com
Accepted: 15 May 2006
We present an analysis of the spatial orientations of 323 galaxies in the cluster Abell 3558. Our aim is to examine non-random effects in galaxy orientations in the subsample of the cluster. The “position angle–inclination” method is used to find the three-dimensional rotation axes. To check for anisotropy or isotropy we carried out three statistical tests: Fourier, Kolmogorov-Smirnov, and Kuiper-V. We assumed a spatially isotropic distribution to examine non-random effects. The galaxies found in the investigated cluster region show isotropy in both two- and three-dimensional analyses of the galactic coordinate system. In addition, it is found that the overall isotropic appearance cannot be maintained when looking at the subsamples. The low radial-velocity galaxies in A 3558 showed anisotropy in both two- and three-dimensional analyses. A weak anisotropy is noticed in the hard X-ray emission region. Few subsamples shows similar alignments with respect to both the galactic and Supergalactic coordinate systems. We offer possible explanations of these anisotropies.
Key words: galaxies: clusters: general / galaxies: evolution / galaxies: spiral / galaxies: distances and redshifts / galaxies: formation / galaxies: statistics
© ESO, 2006