Impeding Turbulence Decay in Self-gravitating Cloud Cores

TL;DR

This paper investigates how self-gravity and turbulent compression influence turbulence decay in molecular cloud cores, revealing that core formation energy can sustain turbulence levels, challenging previous assumptions about turbulence decay.

Contribution

It demonstrates that the diffuse cloud volume controls overall turbulence decay, while dense cores can maintain turbulence through gravitational energy release, a phenomenon absent without self-gravity.

Findings

Dense cores sustain near-zero decay rates.

Gravitational potential energy from core formation maintains turbulence.

Self-gravity influences turbulence persistence in molecular clouds.

Abstract

Turbulence governs the fragmentation of molecular clouds and plays a pivotal role in star formation. The persistence of observed cloud turbulence suggests it does not decay significantly within the turnover timescale, implying a recurrent driving mechanism. Although ubiquitous self-gravity is a plausible driver, MHD simulations by \citet{ostriker2001density} demonstrated that self-gravity alone does not modify the global turbulence decay rate. In this study, we demonstrate that the dominant diffuse volume of a cloud dictates its overall decay rate, while individual dense cores can maintain near-zero decay rates. Crucially, this phenomenon is absent in control simulations excluding self-gravity. This discrepancy cannot be attributed to contamination of turbulent velocities by core contraction, as most cores in our simulations remain in a quasi-equilibrium state. Our analysis reveals that the gravitational potential energy released during core formation\textemdash not necessarily driven by self-gravity but also by turbulent compression\textemdash is sufficient to sustain the observed turbulence levels within cores.