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Astron. Astrophys. 364, L97-L100 (2000)

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Letter to the Editor

Comments on the expected isotropic distribution curves in galaxy orientation studies

B. Aryal and W. Saurer

Institut für Astrophysik der Leopold-Franzens-Universität, Innsbruck, Technikerstrasse 25, 6020 Innsbruck, Austria (binil.aryal@uibk.ac.at & walter.saurer@uibk.ac.at)

Received 16 October 2000 / Accepted 16 November 2000


We present results of random simulations for the expected isotropic distributions of the polar and azimuthal angles of galaxy rotation axes. It is found that selection effects concerning position and inclination of galaxies can remarkably change the shape of these distributions. Selection effects of this kind may play an important role when galaxies are taken from an incomplete dataset (e.g. from a limited region of the sky). These effects can lead to artificial structures (and hence to misinterpretations, as it already happened in the literature) and should be taken into account when deciding upon isotropy or anisotropy in the spatial distribution of spin vectors of galaxies. In this paper we discuss the various effects of selection.

Key words: galaxies: clusters: general – galaxies: general – galaxies: statistics – catalogs

Send offprint requests to: B. Aryal

© European Southern Observatory (ESO) 2000

Online publication: January 29, 2001