Stationary fluid models for the extra-planar gas in spiral galaxies

Abstract

We show how to construct families of stationary hydrodynamical configurations that reproduce the observed vertical gradient of the rotation velocity of the extra-planar gas in spiral galaxies. We then present a simple model for the lagging halo of the spiral galaxy NGC 891, which is in agreement with the HI observations. Our method is based on well known properties of baroclinic solutions, and it is an elementary application of a much more general and flexible method.Comment: 8 pages, 2 figures. Proceedings of the Conference "Extra-planar gas", ASP Conf. Series, R. Braun e