Probing fragmentation and velocity sub-structure in the massive NGC 6334
  filament with ALMA
  Herschel surveys of Galactic clouds support a paradigm for low-mass star
formation in which dense filaments play a crucial role. The detailed
fragmentation properties of star-forming filaments remain poorly understood,
however, and the validity of the filament paradigm in the high-mass regime is
still unclear. To investigate the density/velocity structure of the filament in
the high-mass star-forming region NGC6334, we conducted ALMA observations in
the 3mm continuum and the N2H+(1-0) line at ~3arcsec resolution. The filament
was detected in both tracers. We identified 26 cores at 3mm and 5
velocity-coherent fiber-like features in N2H+ within the filament. The typical
length of, and velocity difference between, the fiber-like features of the
NGC6334 filament are reminiscent of the properties for the fibers of the
low-mass star-forming filament B211/B213. Only 2 or 3 of the 5
velocity-coherent features are well aligned with the filament and may represent
genuine, fiber sub-structures. The core mass distribution has a peak at
~10Msun. They can be divided into 7 groups of cores, closely associated with
ArTeMiS clumps. The projected separation between cores and the projected
spacing between clumps are roughly consistent with the effective Jeans length
in the filament and a physical scale of about 4 times the filament width,
respectively, suggesting a bimodal filament fragmentation process. Despite
being one order of magnitude denser and more massive than the B211/B213
filament, the NGC6334 filament has a similar density/velocity structure. The
difference is that the cores in NGC6334 appear to be an order of magnitude
denser and more massive than the cores in Taurus. This suggests that dense
filaments may evolve and fragment in a similar manner in low- and high-mass
star-forming regions, and that the filament paradigm may hold in the
intermediate-mass (if not high-mass) star formation regime.
