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          Institute: MPI für Astronomie     Collection: Publikationen_mpia     Display Documents

ID: 730399.0, MPI für Astronomie / Publikationen_mpia
Filament fragmentation in high-mass star formation
Authors:Beuther, H.; Ragan, S. E.; Johnston, K.; Henning, T.; Hacar, A.; Kainulainen, J. T.
Date of Publication (YYYY-MM-DD):2015
Title of Journal:Astronomy and Astrophysics
Start Page:id. A67 (12 pp)
Audience:Not Specified
Abstract / Description:Context. Filamentary structures in the interstellar medium are crucial ingredients of the star formation process. They fragment to form individual star-forming cores, and at the same time they may also funnel gas toward the central gas cores, providing an additional gas reservoir. <BR /> Aims: We want to resolve the length scales for filament formation and fragmentation (resolution ≤0.1 pc), in particular the Jeans length and cylinder fragmentation scale. <BR /> Methods: We have observed the prototypical high-mass star-forming filament IRDC 18223 with the Plateau de Bure Interferometer (PdBI) in the 3.2 mm continuum and N2H+(1-0) line emission in a ten-field mosaic at a spatial resolution of ~ 4'' (~14 000 au). <BR /> Results: The dust continuum emission resolves the filament into a chain of at least 12 relatively regularly spaced cores. The mean separation between cores is ~0.40(± 0.18) pc. While this is approximately consistent with the fragmentation of an infinite, isothermal, and gravitationally bound gas cylinder, a high mass-to-length ratio of M/l ≈ 1000 M pc-1 requires additional turbulent and/or magnetic support against radial collapse of the filament. The N2H+(1-0) data reveal a velocity gradient perpendicular to the main filament. Although rotation of the filament cannot be excluded, the data are also consistent with the main filament being comprised of several velocity-coherent subfilaments. Furthermore, this velocity gradient perpendicular to the filament resembles results toward Serpens south that are interpreted as signatures of filament formation within magnetized and turbulent sheet-like structures. Lower-density gas tracers ([CI] and C18O) reveal a similar red- and blueshifted velocity structure on scales around 60'' east and west of the filament. This may tentatively be interpreted as a signature of the large-scale cloud and the smaller scale filament being kinematically coupled. We do not identify a velocity gradient along the axis of the filament. This may be due to no significant gas flows along the filamentary axis, but it may also be partly caused by a low inclination angle of the filament with respect to the plane of the sky minimizing such a signature. <BR /> Conclusions: The IRDC 18223 3.2 mm continuum data are consistent with thermal fragmentation of a gravitationally bound and compressible gas cylinder. However, the high mass-to-length ratio requires additional support - most likely turbulence and/or magnetic fields - against collapse. The N2H+ spectral line data indicate a kinematic origin of the filament, but we cannot conclusively differentiate whether it has formed out of (pre-existing) velocity-coherent subfilaments, whether magnetized converging gas flows, a larger-scale collapsing cloud, or even whether rotation played a significant role during filament formation. Based on observations carried out with the IRAM Plateau de Bure Interferometer. IRAM is supported by INSU/CNRS (France), MPG (Germany), and IGN (Spain).Final reduced data cubes (FITS) are available at the CDS via anonymous ftp to <A href="http://cdsarc.u-strasbg.fr">http://cdsarc.u-strasbg.fr</A> ( or via <A href="http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/584/A67">http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/584/A67</A>
Free Keywords:stars: formation; stars: early-type; stars: individual: IRDC 18223; stars: massive; ISM: clouds; ISM: structure
External Publication Status:published
Document Type:Article
Communicated by:N. N.
Affiliations:MPI für Astronomie
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