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Buckling bars in face-on galaxies observed with MaNGA

Published onAug 03, 2020
Buckling bars in face-on galaxies observed with MaNGA

Over half of disk galaxies are barred, yet the mechanisms for bar formation and the life-time of bar buckling remain poorly understood. In simulations, a thin bar undergoes a rapid (<1 Gyr) event called “buckling”, during which the bar is asymmetrically bent out of the galaxy plane. The inner part of the bar eventually thickens and develops a peanut/X-shaped profile when viewed side-on. We use numerical simulations to develop kinematic diagnostic criteria for identifying the buckling instability. Through analyzing stellar kinematics of N-body model snapshots of a galaxy before, during, and after the buckling phase, we confirm a distinct quadrupolar pattern of out-of-plane stellar velocities. The signature is visible for face-on galaxies with inclinations up to 50 degrees. These hallmarks of buckling allow us to identify five candidates of currently buckling bars in galaxies within the Mapping Nearby Galaxies at Apogee Point Observatory (MaNGA) survey, in near face-on orientations. The frequency of buckling events detected is consistent with the 0.5–1 Gyr timescale predicted by simulations. The five candidates we present more than triple the total number of candidate buckling bars, and are the only ones found using the kinematic signature.

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