Planar distribution of the galaxies in the Local Group

Abstract

AbstractAdopting known data on positions and distances, we make use of analytical geometry and look for the plane that minimizes the distances of all galaxies to it. A planar distribution is found. We apply Hamilton's principle of minimum action to investigate the dynamics of the two major systems of the Local Group, the Milky Way and Andromeda, under the action of forces exerted by nearby galaxies or groups external to the Local Group. We find that the planar distribution is fully compatible with the minimum action and that the external force field is likely parallel to the plane. It pulls the galaxies of the Local Group without altering their planar distribution. Special care is paid to evaluate the robustness of this result. We present an explanation in the linear regime of the numerical results based on the compression effect described with the tidal tensor. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)