Spin vector orientations of galaxies in eight Abell clusters of BM type I

Institut für Astrophysik, Universität Innsbruck, Technikerstraße 25, 6020 Innsbruck, Austria e-mail: [binil.aryal; walter.saurer]@uibk.ac.at

Received: 5 May 2004
Accepted: 16 June 2004

Abstract

We present an analysis of the spatial orientations of 1231 galaxies in 8 Abell clusters of BM type I (type I in the Bautz-Morgan system). Our aim is to examine non-random effects in galaxy orientations in the clusters containing centrally located cD galaxies. We used the “position angle-inclination” method to find the polar and azimuthal angles of the galaxy rotation axes. To analyse the distribution of the polar and azimuthal angle of the galaxy rotation axes and to check for anisotropy or isotropy we have carried out three statistical tests: chi-square, Fourier, and auto correlation. We assumed a spatially isotropic distribution to examine non-random effects. It is found that the spin vector orientations of the galaxies in the clusters Abell 42, Abell 1775, Abell 3558 and Abell 3560 tend to lie parallel to the local supercluster plane. The spin vector projections of galaxies in the clusters Abell 42 and Abell 1775 tend to be oriented perpendicular to the Virgo cluster center whereas the clusters Abell 3558 and Abell 3562 tend to point towards the Virgo cluster center. No preferred orientation is noticed in the clusters Abell 401, Abell 2199 and Abell 3556.