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Implication of the Velocity Dispersion Scalings on High-mass Star Formation in Molecular Clouds
Ist Teil von
The Astronomical journal, 2024-05, Vol.167 (5), p.228
Ort / Verlag
Madison: The American Astronomical Society
Erscheinungsjahr
2024
Quelle
EZB Electronic Journals Library
Beschreibungen/Notizen
Abstract
This paper is aimed at exploring the implications of velocity-dispersion scalings on high-mass star formation in molecular clouds, including the scalings of Larson’s linewidth–size (
σ
–
R
) and ratio–mass surface density (
L
– Σ; here
L
=
σ
/
R
0.5
). We have systematically analyzed the
σ
parameter of well-selected 221 massive clumps, complemented with published samples of other hierarchical density structures of molecular clouds over spatial scales of 0.01–10 pc. Those massive clumps are classified into four phases: quiescent, protostellar, H
ii
region, and PDR clumps in an evolutionary sequence. The velocity dispersion of clumps increases overall with the evolutionary sequence, reflecting enhanced stellar feedback in more evolved phases. The relations of
σ
–
R
and
L
– Σ are weak with the clump sample alone, but become evident when combined with others spanning a much wider spatial scales. For
σ
–
R
, its tight relation indicates a kinematic connection between hierarchical density structures, supporting theoretical models of multiscale high-mass star formation. From the
L
– Σ relation, cloud structures can be found to transition from overvirial state (
α
vir
> 2) to subvirial state (
α
vir
< 2) as they become smaller and denser, indicating a possible shift in the governing force from turbulence to gravity. This implies that the multiscale physical process of high-mass star formation hinges on the self-gravity of subvirial molecular clouds. However, the influence of turbulence may not be dismissed until large-scale clouds attain a subvirial state. This is pending confirmation from future multiscale kinematic observations of molecular clouds with uniform observing settings.