A Caltech Library Service

Low Virial Parameters in Molecular Clouds: Implications for High Mass Star Formation and Magnetic Fields

Kauffmann, Jens and Pillai, Thushara and Goldsmith, Paul F. (2013) Low Virial Parameters in Molecular Clouds: Implications for High Mass Star Formation and Magnetic Fields. Astrophysical Journal, 779 (2). Art. No. 185. ISSN 0004-637X. doi:10.1088/0004-637X/779/2/185.

PDF - Submitted Version
See Usage Policy.

PDF - Published Version
See Usage Policy.


Use this Persistent URL to link to this item:


Whether or not molecular clouds and embedded cloud fragments are stable against collapse is of utmost importance for the study of the star formation process. Only "supercritical" cloud fragments are able to collapse and form stars. The virial parameter, α=M_(vir)/M, which compares the virial to the actual mass, provides one way to gauge stability against collapse. Supercritical cloud fragments are characterized by α≾2, as indicated by a comprehensive stability analysis considering perturbations in pressure and density gradients. Past research has suggested that virial parameters α≳2 prevail in clouds. This would suggest that collapse towards star formation is a gradual and relatively slow process, and that magnetic fields are not needed to explain the observed cloud structure. Here, we review a range of very recent observational studies that derive virial parameters <<2 and compile a catalogue of 1325 virial parameter estimates. Low values of alpha are in particular observed for regions of high mass star formation (HMSF). These observations may argue for a more rapid and violent evolution during collapse. This would enable "competitive accretion" in HMSF, constrain some models of "monolithic collapse", and might explain the absence of high--mass starless cores. Alternatively, the data could point at the presence of significant magnetic fields ~1 mG at high gas densities. We examine to what extent the derived observational properties might be biased by observational or theoretical uncertainties. For a wide range of reasonable parameters, our conclusions appear to be robust with respect to such biases.

Item Type:Article
Related URLs:
URLURL TypeDescription Paper
Goldsmith, Paul F.0000-0002-6622-8396
Additional Information:© 2013 American Astronomical Society. Received 2013 May 16; accepted 2013 August 2; published 2013 December 4. We are grateful to a very constructive and helpful anonymous referee with attention to detail. The reports significantly helped to improve the readability of the paper, and also helped to streamline some of the quantitative arguments presented in this work. We thank Christopher F. McKee, Jonathan Tan, and Matthew Bate for reading and commenting on our manuscript in advance of publication; Marion Wienen for kindly providing data before publication; and Kostas Tassis for enlightening discussions on magnetic fields in SF regions. We like to thank further colleagues who helped to develop this paper over several stages: Fumitaka Nakamura, Norman Murray, Fred C. Adams, and Tom Megeath. JK acknowledges support from the NASA Astrophysics Data Analysis program. This paper benefited from invitations of TP and JK to: the 2012 ASTROWIN workshop at the University of Florida at Gainesville, organized by Jonathan Tan; the 2012 Star Formation Winter School held at the National Astronomical Observatory of Japan (NAOJ) in Tokyo, organized by Fumitaka Nakamura; and Caltech’s Red Door Caffee. TP and JK dedicate this paper to the memory of KSS.
Funding AgencyGrant Number
NASA Astrophysics Data Analysis ProgramUNSPECIFIED
Subject Keywords:ISM: clouds; methods: data analysis; stars: formation
Issue or Number:2
Record Number:CaltechAUTHORS:20130909-080914985
Persistent URL:
Official Citation: Low Virial Parameters in Molecular Clouds: Implications for High-mass Star Formation and Magnetic Fields Jens Kauffmann et al. 2013 ApJ 779 185
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:41157
Deposited By: Tony Diaz
Deposited On:17 Sep 2013 23:31
Last Modified:10 Nov 2021 04:26

Repository Staff Only: item control page