We report the detection of a wing component in NH _ { 3 } emission toward the starless core TUKH122 with subthermal turbulence in the Orion A cloud .
This NH _ { 3 } core is suggested to be on the verge of star formation because the turbulence inside the NH _ { 3 } core is almost completely dissipated , and also because it is surrounded by CCS , which resembles the prestellar core L1544 in Taurus showing infall motions .
Observations were carried out with the Nobeyama 45 m telescope at 0.05 km s ^ { -1 } velocity resolution .
We find that the NH _ { 3 } line profile consists of two components .
The quiescent main component has a small linewidth of 0.3 km s ^ { -1 } dominated by thermal motions , and the red-shifted wing component has a large linewidth of 1.36 km s ^ { -1 } representing turbulent motions .
These components show kinetic temperatures of 11 K and < 30 K , respectively .
Furthermore , there is a clear velocity offset between the NH _ { 3 } quiescent gas ( V _ { LSR } = 3.7 km s ^ { -1 } ) and the turbulent gas ( V _ { LSR } = 4.4 km s ^ { -1 } ) .
The centroid velocity of the turbulent gas corresponds to that of the surrounding gas traced by the ^ { 13 } CO ( J = 1 - 0 ) and CS ( J = 2 - 1 ) lines .
LVG model calculations for CS and CO show that the turbulent gas has a temperature of 8 - 13 K and an H _ { 2 } density of \sim 10 ^ { 4 } cm ^ { -3 } , suggesting that the temperature of the turbulent component is also \sim 10 K. The detections of both NH _ { 3 } quiescent and wing components may indicate a sharp transition from the turbulent parent cloud to the quiescent dense core .