Abstract
Herschel observations of nearby molecular clouds suggest that interstellar filaments and prestellar cores represent two fundamental steps in the star formation process. The observations support a picture of low-mass star formation according to which ~ 0.1 pc-wide filaments form first in the cold interstellar medium, probably as a result of large-scale compression of interstellar matter by supersonic turbulent flows, and then prestellar cores arise from gravitational fragmentation of the densest filaments. Whether this scenario also applies to regions of high-mass star formation is an open question, in part because Herschel data cannot resolve the inner width of filaments in the nearest regions of massive star formation. We used the bolometer camera ArTeMiS on the APEX telescope to map the central part of the NGC6334 complex at a factor of > 3 higher resolution than Herschel at 350 microns. Combining ArTeMiS data with Herschel data allowed us to study the structure of the main filament of the complex with a resolution of 8" or < 0.07 pc at d ~ 1.7 kpc. Our study confirms that this filament is a very dense, massive linear structure with a line mass ranging from ~ 500 Msun/pc to ~ 2000 Msun/pc over nearly 10 pc. It also demonstrates that its inner width remains as narrow as W ~ 0.15 +- 0.05 pc all along the filament length, within a factor of < 2 of the characteristic 0.1 pc value found with Herschel for lower-mass filaments in the Gould Belt. While it is not completely clear whether the NGC 6334 filament will form massive stars or not in the future, it is two to three orders of magnitude denser than the majority of filaments observed in Gould Belt clouds, and yet has a very similar inner width. This points to a common physical mechanism for setting the filament width and suggests that some important structural properties of nearby clouds also hold in high-mass star forming regions.
Highlights
This publication is based on data acquired with the Atacama Pathfinder Experiment (APEX) in ESO program 091.C-0870
The observations support a picture of low-mass star formation according to which filaments of ∼0.1 pc width form first in the cold interstellar medium, probably as a result of large-scale compression of interstellar matter by supersonic turbulent flows, and prestellar cores arise from gravitational fragmentation of the densest filaments
Our study confirms that this filament is a very dense, massive linear structure with a line mass ranging from ∼500 M /pc to ∼2000 M /pc over nearly 10 pc
Summary
This publication is based on data acquired with the Atacama Pathfinder Experiment (APEX) in ESO program 091.C-0870. A possible manifestation of such MHD waves may have been found in the form of braided velocity-coherent substructure in the Taurus B211–3 filament (Hacar et al 2013) Another major result from Herschel in nearby clouds is that most (>75%) lowmass prestellar cores and protostars are found in dense, supercritical filaments for which the mass per unit length Mline exceeds the critical line mass of nearly isothermal long cylinders Könyves et al 2015) These Herschel findings support a scenario for low-mass star formation in two main steps (cf André et al 2014): First, large-scale compression of interstellar material in supersonic MHD flows generates a cobweb of filaments ∼0.1 pc in width in the ISM; second, the densest filaments fragment into prestellar cores (and subsequently protostars) by gravitational instability above Mline,crit, while simultaneously growing in mass through accretion of background cloud material.
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