http://arxiv.org/abs/1712.00430
(X/peanut)-shaped features observed in a significant fraction of disk galaxies are thought to have formed from vertically buckled bars. Despite being three dimensional structures, they are preferentially detected in near edge-on projection. Only a few galaxies are found to have displayed such structures when their disks are relatively face-on – suggesting that either they are generally weak in face-on projection or many may be hidden by the light of their galaxy’s face-on disk.
Here we report on three (collisionless) simulated galaxies displaying peanut-shaped structures when their disks are seen both face-on and edge-on – resembling a three-dimensional peanut or dumbbell. Furthermore, these structures are accompanied by ansae and an outer ring at the end of the bar — as seen in real galaxies such as IC~5240.
The same set of quantitative parameters used to measure peanut structures in real galaxies have been determined for the simulated galaxies, and a broad agreement is found. In addition, the peanut length grows in tandem with the bar, and is a maximum at half the length of the bar. Beyond the cutoff of these peanut structures, towards the end of the bar, we discover a new positive/negative feature in the $B_6$ radial profile associated with the isophotes of the ansae/ring.
Our simulated, self-gravitating, three-dimensional peanut structures display cylindrical rotation even in the near-face-on disk projection. In addition, we report on a kinematic pinch in the velocity map along the bar minor-axis, matching that seen in the surface density map.
K. Saha, A. Graham and I. Rodriguez-Herranz
Mon, 4 Dec 17
29/72
Comments: 14 pages, 16 figures, 3 tables, accepted for publication in ApJ
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