Journal Article

The lifetimes of spiral patterns in disc galaxies

J. A. Sellwood

in Monthly Notices of the Royal Astronomical Society

Published on behalf of The Royal Astronomical Society

Volume 410, issue 3, pages 1637-1646
Published in print January 2011 | ISSN: 0035-8711
Published online January 2011 | e-ISSN: 1365-2966 | DOI: http://dx.doi.org/10.1111/j.1365-2966.2010.17545.x
The lifetimes of spiral patterns in disc galaxies

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The rate of internally driven evolution of galaxy discs is strongly affected by the lifetimes of the spiral patterns they support. Evolution is much faster if the spiral patterns are recurrent short-lived transients rather than long-lived, quasi-steady features. As rival theories are still advocated based on these two distinct hypotheses, I review the evidence that bears on the question of the lifetimes of spiral patterns in galaxies. Observational evidence from external galaxies is frustratingly inconclusive, but the velocity distribution in the solar neighbourhood is more consistent with the transient picture. I present simulations of galaxy models that have been proposed to support quasi-steady, two-arm spiral modes that in fact evolve quickly due to multi-arm instabilities. I also show that all simulations to date manifest short-lived patterns, despite claims to the contrary. Thus the transient hypothesis is favoured by both numerical results and the velocity distribution in the solar neighbourhood.

Keywords: instabilities; galaxies: evolution; galaxies: kinematics and dynamics; galaxies: spiral

Journal Article.  8516 words.  Illustrated.

Subjects: Astronomy and Astrophysics

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