Long-lived transient structure in collisionless self-gravitating systems.

Area of Science:

• Astrophysics
• Computational Physics
• Gravitational Dynamics

Background:

• Self-gravitating systems are typically modeled with two-phase evolution: violent relaxation followed by slow collisional processes.
• Complex galactic structures like spiral arms are often attributed to instabilities or dissipative processes.

Purpose of the Study:

• To investigate if purely self-gravitating systems can form complex, long-lived structures without dissipative interactions.
• To explore the generic formation of nonstationary structures from simple initial configurations.

Main Methods:

• Numerical simulations of self-gravitating systems with varied initial conditions.
• Analysis of system evolution from far-from-equilibrium states.

Main Results:

• Purely self-gravitating systems readily form complex structures, including spiral arms, bars, and ringlike features.
• These structures are long-lived but transient, existing between dynamical and collisional timescales.
• Systems exhibit a flattened, rotating region around a virialized triaxial core with radial motions in outer parts.

Conclusions:

• Gravitational relaxation alone can generate intricate, nonstationary structures in self-gravitating systems.
• These findings challenge the necessity of dissipative processes for forming galactic morphology.
• The study provides simple models relevant to understanding real galaxy structures, highlighting dissipationless formation pathways.