ALMA observations of NGC 6334S. II. Subsonic and Transonic Narrow
  Filaments in a High-mass Star Formation Cloud
  We present a study of narrow filaments toward a massive infrared dark cloud,
NGC 6334S, using the Atacama Large Millimeter/submillimeter Array (ALMA).
Thirteen gas filaments are identified using the H$^{13}$CO$^{+}$ line, while a
single continuum filament is revealed by the continuum emission. The filaments
present a compact radial distribution with a median filament width of
$\sim$0.04 pc narrower than the previously proposed `quasi-universal' 0.1~pc
filament width. The higher spatial resolution observations and higher-density
gas tracer tend to identify even narrower and lower mass filaments. The
filament widths are roughly twice the size of embedded cores. The gas filaments
are largely supported by thermal motions. The nonthermal motions are
predominantly subsonic and transonic in both identified gas filaments and
embedded cores, which may imply that stars are likely born in environments of
low turbulence. A fraction of embedded objects show a narrower velocity
dispersion compared with their corresponding natal filaments, which may
indicate that the turbulent dissipation is taking place in these embedded
cores. The physical properties (mass, mass per unit length, gas kinematics, and
width) of gas filaments are analogous to those of narrow filaments found in
low- to high-mass star-forming regions. The more evolved sources are found to
be farther away from the filaments, a situation that may have resulted from the
relative motions between the YSOs and their natal filaments.
