Detection of a turbulent gas component associated with a starless core
  with subthermal turbulence in the Orion A cloud
  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 ($VLSR=3.7$ km s$^{-1}$) and the turbulent gas
($VLSR=4.4$ 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 ~ $10^4$
cm$^{-3}$, suggesting that the temperature of the turbulent component is also ~
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.
