Standing solitary waves as transitions to spiral structures in gravitationally unstable accretion disks

TL;DR

This paper investigates how standing solitary waves in gravitationally unstable accretion disks can serve as transitional structures leading to spiral formations and potential fragmentation, providing insight into disk evolution.

Contribution

It introduces a nonlinear dynamical pathway involving standing solitary waves that explains the development of spiral structures in unstable accretion disks.

Findings

Standing solitary waves exist as localized solutions in the disk model.

These solitary waves are unstable to non-axisymmetric perturbations.

Solitary waves may act as a pathway to spiral structures and fragmentation.

Abstract

Astrophysical disks that are sufficiently cold and dense are linearly unstable to the formation of axisymmetric rings as a result of the disk's gravity. In practice, spiral structures are formed, which may in turn produce bound fragments. We study a nonlinear dynamical path that can explain the development of spirals in a local model of a gaseous disk on the subcritical side of the gravitational instability bifurcation. Axisymmetric equilibria can be radially periodic or localized, in the form of standing solitary waves. The solitary solutions have an energy slightly larger than a smooth disk. They are further unstable to non-axisymmetric perturbations with a wide range of azimuthal wavenumbers. The solitary waves may act as a pathway to spirals and fragmentation.