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To study physical properties of the natal filament gas around the cloud coreharboring an exceptionally young low-mass protostar GF9-2, we carried out J=1-0line observations of 12CO, 13CO, and C18O molecules using the Nobeyama 45mtelescope. The mapping area covers ~1/5 of the whole filament. Our 13CO andC18O maps clearly demonstrate that the core formed at the local density maximaof the filament, and the internal motions of the filament gas are totallygoverned by turbulence with Mach number of ~2. We estimated the scale height ofthe filament to be H = 0.3 ~ 0.7 pc, yielding the central density of n_c = 700~4200 cm^-3. Our analysis adopting an isothermal cylinder model shows that thefilament is supported by the turbulent and magnetic pressures against theradial and axial collapse due to self-gravity. Since both the dissipation timescales of the turbulence and the transverse magnetic fields can be comparableto the free-fall time of the filament gas of 10^6 years, we conclude that thelocal decay of the supersonic turbulence made the filament gas locallyunstable, hence making the core collapse. Furthermore, we newly detected a gascondensation with velocity width enhancement to ~0.3 pc south-west of the GF9-2core. The condensation has a radius of ~0.15 pc and an LTE mass of ~5 Msun. Itsinternal motion is turbulent with Mach number of ~3, suggestive of agravitationally unbound state. Considering the uncertainties in our estimates,however, we propose that the condensation is a precursor of a cloud core whichwould have been produced by the collision of the two gas components identifiedin the filament.

A Dynamically Collapsing Core and a Precursor of a Core in a Filament Supported by Turbulent and Magnetic Pressures