Are Massive Dense Clumps Truly Subvirial? A New Analysis Using Gould Belt Ammonia Data

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 l...

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Published in:The Astrophysical journal 2021-11, Vol.922 (1), p.87
Main Authors: Singh, Ayushi, Matzner, Christopher D., Friesen, Rachel K., Martin, Peter G., Pineda, Jaime E., Rosolowsky, Erik, Alves, Felipe, Chacón-Tanarro, Ana, Chen, Hope How-Huan, Chen, Michael Chun-Yuan, Choudhury, Spandan, Di Francesco, James, Keown, Jared, Kirk, Helen, Punanova, Anna, Seo, Youngmin, Shirley, Yancy, Ginsburg, Adam, Offner, Stella S. R., Arce, Héctor G., Caselli, Paola, Goodman, Alyssa A., Myers, Philip C., Redaelli, Elena
Format: Article
Language:English
Subjects:
Ammonia
Astronomy data analysis
Astrophysics
Belts
Clouds
Clumps
Dust emission
Interstellar dynamics
Kinetic energy
Molecular clouds
Systematic errors
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Summary: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 reexamine 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 overcorrecting 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 subvirial ones. As a by-product, we present a catalog of masses, energies, and virial energy ratios for 85 Gould Belt clumps.
ISSN:0004-637X
1538-4357
DOI:10.3847/1538-4357/ac20d2