Morphological dependence in the spatial orientations of Local Supercluster galaxies

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

Received: 16 July 2004
Accepted: 8 November 2004

Abstract

We have compiled a database of 4073 morphologically identified galaxies with radial velocity <3000 km s^-1 and examined the alignments of the spin vectors of these galaxies in the Local Supercluster (LSC). Our aim is to test the morphological dependence of galaxy orientation. The “position angle – inclination” method is used to find the polar and azimuthal angles of the galaxy rotation axes. The spatial isotropic distribution is assumed to examine the non-random effects. We have carried out chi-square, Fourier, and auto correlation tests to examine non-random effects in the distributions of the polar and azimuthal angles of the galaxy rotation axes. We suspect that the orientations of galaxies in the LSC could be closely related to galactic morphology. The spiral galaxies exhibit anisotropy although not at a very high significance level. It is found that the spin vector orientations of the spiral galaxies in the LSC tend to lie perpendicular to the LSC plane. No preferred orientation is found in the spin vector orientations of barred spiral and irregular galaxies. The orientations of early-type and late-type spirals and barred spirals are discussed.