The Stability of Some Galaxy Disks is Still Perplexing

The problem of how some disk galaxies avoid forming bars remains unsolved. Many galaxy models having reasonable properties continue to manifest vigorous instabilities that rapidly form strong bars and no widely accepted idea has yet been advanced to account for how some disk galaxies manage to avoid...

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Bibliographic Details
Published in:The Astrophysical journal 2023-12, Vol.958 (2), p.182
Main Authors: Sellwood, J. A., Carlberg, R. G.
Format: Article
Language:English
Subjects:
Astronomical models
Astrophysics
Corotation
Disk galaxies
Dynamic stability
Feedback loops
Galaxy dynamics
Galaxy evolution
Galaxy structure
Spiral galaxies
Standing waves
Stars & galaxies
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Summary:The problem of how some disk galaxies avoid forming bars remains unsolved. Many galaxy models having reasonable properties continue to manifest vigorous instabilities that rapidly form strong bars and no widely accepted idea has yet been advanced to account for how some disk galaxies manage to avoid this instability. It is encouraging that not all galaxies formed in recent cosmological simulations possess bars, but the dynamical explanation for this result is unclear. The unstable mode that creates a bar is understood as a standing wave in a cavity that reflects off the disk center and the corotation radius, with amplification at corotation. Here we use simulations to address one further idea that may inhibit the feedback loop and therefore contribute to stability, which is to make the disk center dynamically hot and/or to taper away mass from the inner disk, which could be masked by a bulge. Unfortunately, we find that neither strategy makes much difference to the global stability of the disk in the models we have tried. While deep density cutouts do indeed prevent feedback through the center, they still reflect incoming waves and thereby provoke a slightly different instability that again leads to a strong bar.
ISSN:0004-637X
1538-4357
DOI:10.3847/1538-4357/acf9ee