Transient spirals as superposed instabilities

Abstract

We present evidence that recurrent spiral activity, long manifested in simulations of disk galaxies, results from the super-position 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.

Includes proof corrections. To appear in ApJ, 13 pages, 11 figures. A version with full resolution figures is available at http://www.physics.rutgers.edu/~sellwood/modes.pdf

References in corpus (3)

• Kinematics of Spiral Arm Streaming in M51
• The statistics of the subhalo abundance of dark matter haloes
• On the galaxy spiral arms' nature as revealed by rotation frequencies

Cited by in corpus (17)

• Dawes Review 4: Spiral Structures in Disc Galaxies
• The effect of radial migration on galactic disks
• The Rich Are Different: Evidence from the RAVE Survey for Stellar Radial Migration
• 24.77 Pflops on a Gravitational Tree-Code to Simulate the Milky Way Galaxy with 18600 GPUs
• Gas and Stellar Motions and Observational Signatures of Co-Rotating Spiral Arms
• The Vertical Structure and Kinematics of Grand Design Spirals
• Spiral structure in nearby galaxies II. comparative analysis and conclusions
• Constraints on Radial Migration in Spiral Galaxies I. Analytic Criterion for Capture at Corotation
• Tracing the Galactic spiral structure with embedded clusters
• The stellar kinematics of co-rotating spiral arms in Gaia mock observations
• Feathering Instability of Spiral Arms. II. Parameter Study
• Detection of periodic variations in vertical velocities of Galactic masers
• Smoothing Rotation Curves and Mass Profiles
• Lindblad Zones: resonant eccentric orbits to aid bar and spiral formation in galaxy discs
• The RINGS Survey I: Halpha and HI Velocity Maps of Galaxy NGC 2280
• Bisymmetric normal modes in soft-centred and realistic galactic discs
• Spiral Density Waves in M81. II. Hydrodynamic Simulations for Gas Response to Stellar Spiral Density Waves