We present the results of mapping observations toward a nearby starless filamentary cloud , the Taurus Molecular Cloud 1 ( TMC-1 ) , in the CCS ( J _ { N } = 4 _ { 3 } -3 _ { 2 } , 45.379033 GHz ) emission line , using the Nobeyama 45-m telescope .
The map shows that the TMC-1 filament has a diameter of \sim 0.1 pc and a length of \sim 0.5 pc at a distance of 140 pc .
The position-velocity diagrams of CCS clearly indicate the existence of velocity-coherent substructures in the filament .
We identify 21 substructures that are coherent in the position-position-velocity space by eye .
Most of the substructures are elongated along the major axis of the TMC-1 filament .
The line densities of the subfilaments are close to the critical line density for the equilibrium ( \sim 17 M _ { \sun } pc ^ { -1 } for the excitation temperature of 10 K ) , suggesting that self-gravity should play an important role in the dynamics of the subfilaments .