The Evolution of Cloud Cores and the Formation of Stars

TL;DR

This paper explores how large-amplitude oscillations in starless cores influence their evolution and observational appearance, suggesting oscillation decay timescales regulate core lifetimes and star formation, challenging magnetic field assumptions.

Contribution

It introduces a hydrodynamic model showing that core oscillations significantly impact stability, evolution, and observational features without needing magnetic fields.

Findings

Oscillations support cores and delay collapse.

Core lifetimes are limited by oscillation decay (~10^5-10^6 years).

Oscillations can cause asymmetric observations and stability misclassification.

Abstract

For a number of starless cores, self-absorbed molecular line and column density observations have implied the presence of large-amplitude oscillations. We examine the consequences of these oscillations on the evolution of the cores and the interpretation of their observations. We find that the pulsation energy helps support the cores and that the dissipation of this energy can lead toward instability and star formation. In this picture, the core lifetimes are limited by the pulsation decay timescales, dominated by non-linear mode-mode coupling, and on the order of ~few x 10^5--10^6 yr. Notably, this is similar to what is required to explain the relatively low rate of conversion of cores into stars. For cores with large-amplitude oscillations, dust continuum observations may appear asymmetric or irregular. As a consequence, some of the cores that would be classified as supercritical may be dynamically stable when oscillations are taken into account. Thus, our investigation motivates a simple hydrodynamic picture, capable of reproducing many of the features of the progenitors of stars without the inclusion of additional physical processes, such as large-scale magnetic fields.