On the formation of warped gas discs in galaxies

Abstract

Abstract We consider the most commonly occurring circumstances which apply to galaxies, namely membership in galaxy groups of about 1013 h−1 M⊙ total mass, and estimate the accompanying physical conditions of intergalactic medium (IGM) density and the relative galaxy–IGM space velocity. We then investigate the dynamical consequences of such a typical galaxy–IGM interaction on a rotating gaseous disc within the galaxy potential. We find that the rotating outer disc is systematically distorted into a characteristic ‘warp’ morphology, of the type that has been well-documented in the majority of well-studied nearby systems. The distortion is established rapidly, within 2 rotation periods, and is long-lived, surviving for at least 10. A second consequence of the interaction is the formation of a one-arm retrograde spiral wave pattern that propagates in the disc. We suggest that the ubiquity of the warp phenomenon might be used to reconstruct both the IGM density profile and individual member orbits within galaxy groups.