Annular structures in perturbed low mass disc-shaped gaseous nebulae I : general and standard models

TL;DR

This paper analytically investigates how small radial perturbations in low mass, rotating gaseous discs can lead to the formation of annular structures, with results applicable to various astrophysical disc systems.

Contribution

It provides the first analytical solutions for perturbed low mass gaseous discs, revealing conditions for annular structure formation due to radial perturbations.

Findings

Perturbed specific mass shows exponentially spaced maxima.

Distance ratio of maxima depends on disc properties and perturbation frequency.

Radial flows are induced, potentially forming gaseous annular structures.

Abstract

Abstract This is the first of two papers where we study analytical solutions of a bidimensional low mass gaseous disc slowly rotating around a central mass and submitted to small radial periodic perturbations. Hydrodynamics equations are solved for the equilibrium and perturbed configurations. A wave-like equation for the gas perturbed specific mass is deduced and solved analytically for several cases of exponents of the power law distributions of the unperturbed specific mass and sound speed. It is found that, first, the gas perturbed specific mass displays exponentially spaced maxima, corresponding to zeros of the radial perturbed velocity; second, the distance ratio of successive maxima of the perturbed specific mass is a constant depending on disc characteristics and, following the model, also on the perturbation's frequency; and, third, inward and outward gas flows are induced from zones of minima toward zones of maxima of perturbed specific mass, leading eventually to the possible formation of gaseous annular structures in the disc. The results presented may be applied in various astrophysical contexts to slowly rotating thin gaseous discs of negligible relative mass, submitted to small radial periodic perturbations.