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arXiv · 1909.10291

The evolution of pitch angles of spiral arms

J. E. Pringle·C. L. Dobbs
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Abstract

In spiral galaxies, the pitch angle, $α$, of the spiral arms is often proposed as a discriminator between theories for the formation of the spiral structure. In Lin-Shu density wave theory, $α$ stays constant in time, being simply a property of the underlying galaxy. In other theories (e.g tidal interaction, self-gravity) it is expected that the arms wind up in time, so that to a first approximation $\cot α\propto t$. For these theories, it would be expected that a sample of galaxies observed at random times should show a uniform distribution of $\cot α$. We show that a recent set of measurements of spiral pitch angles (Yu & Ho 2018) is broadly consistent with this expectation.

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J. E. Pringle, C. L. Dobbs. 2019-09-23. The evolution of pitch angles of spiral arms. https://doi.org/10.1093/mnras%2Fstz2694

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