Oscillating Starless Cores: The Nonlinear Regime

TL;DR

This paper uses 3D hydrodynamic simulations to study oscillations in starless cores, revealing that nonlinear mode-coupling causes slow damping over millions of years, consistent with observed core lifetimes.

Contribution

It introduces a nonlinear simulation approach to analyze the stability and damping of oscillations in thermally-supported starless cores, extending previous linear analyses.

Findings

Oscillations are damped mainly by nonlinear mode-coupling.

Damping timescales are on the order of a few million years.

Oscillations can persist over the observed lifetimes of globules.

Abstract

In a previous paper, we modeled the oscillations of a thermally-supported (Bonnor-Ebert) sphere as non-radial, linear perturbations following a standard analysis developed for stellar pulsations. The predicted column density variations and molecular spectral line profiles are similar to those observed in the Bok globule B68 suggesting that the motions in some starless cores may be oscillating perturbations on a thermally supported equilibrium structure. However, the linear analysis is unable to address several questions, among them the stability, and lifetime of the perturbations. In this paper we simulate the oscillations using a three-dimensional numerical hydrodynamic code. We find that the oscillations are damped predominantly by non-linear mode-coupling, and the damping time scale is typically many oscillation periods, corresponding to a few million years, and persisting over the inferred lifetime of gobules.