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Title: Transient spirals as superposed instabilities

We present evidence that recurrent spiral activity, long manifested in simulations of disk galaxies, results from the superposition of a few transient spiral modes. Each mode lasts between 5 and 10 rotations at its corotation radius where its amplitude is greatest. The scattering of stars as each wave decays takes place over narrow ranges of angular momentum, causing abrupt changes to the impedance of the disk to subsequent traveling waves. Partial reflections of waves at these newly created features allows new standing-wave instabilities to appear that saturate and decay in their turn, scattering particles at new locations, creating a recurring cycle. The spiral activity causes the general level of random motion to rise, gradually decreasing the ability of the disk to support further activity unless the disk contains a dissipative gas component from which stars form on near-circular orbits. We also show that this interpretation is consistent with the behavior reported in other recent simulations with low-mass disks.
Authors:
 [1] ;  [2]
  1. Department of Physics and Astronomy, Rutgers University, 136 Frelinghuysen Road, Piscataway, NJ 08854 (United States)
  2. Department of Astronomy and Astrophysics, University of Toronto, Toronto, ON M5S 3H4 (Canada)
Publication Date:
OSTI Identifier:
22357094
Resource Type:
Journal Article
Resource Relation:
Journal Name: Astrophysical Journal; Journal Volume: 785; Journal Issue: 2; Other Information: Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
79 ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; AMPLITUDES; ANGULAR MOMENTUM; DECAY; GALAXIES; INSTABILITY; MASS; ORBITS; RANDOMNESS; REFLECTION; ROTATION; SCATTERING; SIMULATION; STANDING WAVES; STARS; TRANSIENTS; TRAVELLING WAVES