RESONANT CLUMPING AND SUBSTRUCTURE IN GALACTIC DISKS
- Kavli Institute for Astronomy and Astrophysics, Peking University, Yi He Yuan Lu 5, Hai Dian Qu, Beijing 100871 (China)
- Key Laboratory for Research in Galaxies and Cosmology, Shanghai Astronomical Observatory, Chinese Academy of Sciences, 80 Nandan Road, Shanghai 200030 (China)
We describe a method to extract resonant orbits from N-body simulations, exploiting the fact that they close in frames rotating with a constant pattern speed. Our method is applied to the N-body simulation of the Milky Way by Shen et al. This simulation hosts a massive bar, which drives strong resonances and persistent angular momentum exchange. Resonant orbits are found throughout the disk, both close to the bar and out to the very edges of the disk. Using Fourier spectrograms, we demonstrate that the bar is driving kinematic substructure even in the very outer parts of the disk. We identify two major orbit families in the outskirts of the disk, one of which makes significant contributions to the kinematic landscape, namely, the m:l = 3:−2 family, resonating with the bar. A mechanism is described that produces bimodal distributions of Galactocentric radial velocities at selected azimuths in the outer disk. It occurs as a result of the temporal coherence of particles on the 3:−2 resonant orbits, which causes them to arrive simultaneously at pericenter or apocenter. This resonant clumping, due to the in-phase motion of the particles through their epicycle, leads to both inward and outward moving groups that belong to the same orbital family and consequently produce bimodal radial velocity distributions. This is a possible explanation of the bimodal velocity distributions observed toward the Galactic anticenter by Liu et al. Another consequence is that transient overdensities appear and dissipate (in a symmetric fashion), resulting in a periodic pulsing of the disk’s surface density.
- OSTI ID:
- 22522465
- Journal Information:
- Astrophysical Journal, Journal Name: Astrophysical Journal Journal Issue: 2 Vol. 804; ISSN ASJOAB; ISSN 0004-637X
- Country of Publication:
- United States
- Language:
- English
Similar Records
RADIAL MOTIONS IN DISK STARS: ELLIPTICITY OR SECULAR FLOWS?
Exploding satellites—the tidal debris of the ultra-faint dwarf galaxy hercules