Are massive dense clumps truly sub-virial? A new analysis using Gould Belt ammonia data

TL;DR

This study re-evaluates the dynamical state of massive dense clumps in the Gould Belt, showing they are in virial equilibrium when systematic errors are properly accounted for, challenging previous sub-virial conclusions.

Contribution

It introduces a refined analysis method that corrects for common systematic errors, demonstrating that massive Gould Belt clumps are not sub-virial as previously thought.

Findings

Massive Gould Belt clumps are in virial equilibrium.

Systematic errors can bias kinetic-to-gravitational energy ratio estimates.

A catalog of 85 clumps with their energies and virial ratios is provided.

Abstract

Dynamical studies of dense structures within molecular clouds often conclude that the most massive clumps contain too little kinetic energy for virial equilibrium, unless they are magnetized to an unexpected degree. This raises questions about how such a state might arise, and how it might persist long enough to represent the population of massive clumps. In an effort to re-examine the origins of this conclusion, we use ammonia line data from the Green Bank Ammonia Survey and Planck-calibrated dust emission data from Herschel to estimate the masses and kinetic and gravitational energies for dense clumps in the Gould Belt clouds. We show that several types of systematic error can enhance the appearance of low kinetic-to-gravitational energy ratios: insufficient removal of foreground and background material; ignoring the kinetic energy associated with velocity differences across a resolved cloud; and over-correcting for stratification when evaluating the gravitational energy. Using an analysis designed to avoid these errors, we find that the most massive Gould Belt clumps harbor virial motions, rather than sub-virial ones. As a byproduct, we present a catalog of masses, energies, and virial energy ratios for 85 Gould Belt clumps.