Detection of two power-law tails in the probability distribution functions of massive GMCs

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 dist...

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Vydáno v:	Monthly notices of the Royal Astronomical Society Ročník 453; číslo 1; s. L41 - L45
Hlavní autoři:	Schneider, N., Bontemps, S., Girichidis, P., Rayner, T., Motte, F., André, Ph, Russeil, D., Abergel, A., Anderson, L., Arzoumanian, D., Benedettini, M., Csengeri, T., Didelon, P., Francesco, J. Di, Griffin, M., Hill, T., Klessen, R. S., Ossenkopf, V., Pezzuto, S., Rivera-Ingraham, A., Spinoglio, L., Tremblin, P., Zavagno, A.
Médium:	Journal Article
Jazyk:	angličtina
Vydáno:	Oxford University Press 11.10.2015 Oxford University Press (OUP): Policy P - Oxford Open Option A
Témata:	Astrophysics Cosmology and Extra-Galactic Astrophysics Sciences of the Universe ISM: clouds dust, extinction dust extinction
ISSN:	1745-3925, 0035-8711, 1745-3933, 1365-2966
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Popis
Shrnutí:	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 (A V) 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 A V ∼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.
ISSN:	1745-3925 0035-8711 1745-3933 1365-2966
DOI:	10.1093/mnrasl/slv101