Detection of two power-law tails in the probability distribution functions of massive GMCs
Date Issued
2015
Author(s)
Schneider, N.
•
Bontemps, S.
•
Girichidis, P.
•
Rayner, T.
•
Motte, F.
•
André, P.
•
Russeil, D.
•
Abergel, A.
•
Anderson, L.
•
Arzoumanian, D.
•
•
Csengeri, T.
•
Didelon, P.
•
di, Francesco J.
•
Griffin, M.
•
Hill, T.
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Klessen, R. S.
•
Ossenkopf, V.
•
•
Rivera-Ingraham, A.
•
•
Tremblin, P.
•
Zavagno, A.
Abstract
We report the novel detection of complex high column density tails in the probability distribution functions (PDFs) for three high-mass star-forming regions (CepOB3, MonR2, NGC 6334), obtained from dust emission observed with Herschel. The low column density range can be fitted with a lognormal distribution. A first power-law tail starts above an extinction (AV) of ̃6-14. It has a slope of α 1.3-2 for the &ρ ≈ r-α profile for an equivalent density distribution (spherical or cylindrical geometry), and is thus consistent with free-fall gravitational collapse. Above AV ̃40, 60, and 140, we detect an excess that can be fitted by a flatter power-law tail with α > 2. It correlates with the central regions of the cloud (ridges/hubs) of size ̃;1 pc and densities above 104 cm-3. This excess may be caused by physical processes that slow down collapse and reduce the flow of mass towards higher densities. Possible are: (1) rotation, which introduces an angular momentum barrier, (2) increasing optical depth and weaker cooling, (3) magnetic fields, (4) geometrical effects, and (5) protostellar feedback. The excess/second power-law tail is closely linked to high-mass star-formation though it does not imply a universal column density threshold for the formation of (high-mass) stars.
Volume
453
Start page
L41
Issn Identifier
0035-8711
Ads BibCode
2015MNRAS.453L..41S
Rights
open.access
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