To study physical properties of the natal filament gas around the cloud core harboring an exceptionally young low-mass protostar GF 9-2 , we carried out J = 1 - 0 line observations of ^ { 12 } CO , ^ { 13 } CO , and C ^ { 18 } O molecules using the Nobeyama 45 m telescope .
The mapping area covers \sim 1 / 5 of the whole filament .
Our ^ { 13 } CO and C ^ { 18 } O maps clearly demonstrate that the core formed at the local density maxima of the filament , and the internal motions of the filament gas are totally governed by turbulence with Mach number of \sim 2 .
We estimated the scale height of the filament to be H = 0.3 \sim 0.7 pc , yielding the central density of n _ { \mathrm { c } } = 700 \sim 4200 cm ^ { -3 } .
Our analysis adopting an isothermal cylinder model shows that the filament is supported by the turbulent and magnetic pressures against the radial and axial collapse due to self-gravity .
Since both the dissipation time scales of the turbulence and the transverse magnetic fields can be comparable to the free-fall time of the filament gas of 10 ^ { 6 } years , we conclude that the local decay of the supersonic turbulence made the filament gas locally unstable , hence making the core collapse .
Furthermore , we newly detected a gas condensation with velocity width enhancement to \sim 0.3 pc south-west of the GF 9-2 core .
The condensation has a radius of \sim 0.15 pc and an LTE mass of \sim 5 M _ { \odot } .
Its internal motion is turbulent with Mach number of \sim 3 , suggestive of a gravitationally unbound state .
Considering the uncertainties in our estimates , however , we propose that the condensation is a precursor of a cloud core which would have been produced by the collision of the two gas components identified in the filament .