The formation of filamentary bundles in turbulent molecular clouds
  The classical picture of a star-forming filament is a near-equilibrium
structure, with collapse dependent on its gravitational criticality. Recent
observations have complicated this picture, revealing filaments as a mess of
apparently interacting subfilaments, with transsonic internal velocity
dispersions and mildly supersonic intra-subfilament dispersions. How structures
like this form is unresolved. Here we study the velocity structure of
filamentary regions in a simulation of a turbulent molecular cloud. We present
two main findings: first, the observed complex velocity features in filaments
arise naturally in self gravitating hydrodynamic simulations of turbulent
clouds without the need for magnetic or other effects. Second, a region that is
filamentary only in projection and is in fact made of spatially distinct
features can displays these same velocity characteristics. The fact that these
disjoint structures can masquerade as coherent filaments in both projection and
velocity diagnostics highlights the need to continue developing sophisticated
filamentary analysis techniques for star formation observations.
