Warm CO gas generated by possible turbulent shocks in a low-mass
  star-forming dense core in Taurus
  We report ALMA Cycle 3 observations in CO isotopes toward a dense core,
MC27/L1521F in Taurus, which is considered to be at an early stage of multiple
star formation in a turbulent environment. Although most of the high-density
parts of this core are considered to be as cold as $\sim$10 K, high-angular
resolution ($\sim$20 au) observations in $^{12}$CO ($J$ = 3--2) revealed
complex warm ($>$15--60 K) filamentary/clumpy structures with the sizes from a
few tens of au to $\sim$1,000 au. The interferometric observations of $^{13}$CO
and C$^{18}$O show that the densest part with arc-like morphologies associated
with the previously identified protostar and condensations are slightly
redshifted from the systemic velocity of the core. We suggest that the warm CO
clouds may be consequences of shock heating induced by interactions among the
different density/velocity components that originated from the turbulent
motions in the core. However, such a small-scale and fast turbulent motion does
not correspond to a simple extension of the line-width-size relation (i.e.,
Larson'{}s law), and thus the actual origin remains to be studied. The
high-angular resolution CO observations are expected to be essential in
detecting small-scale turbulent motions in dense cores and to investigate
protostar formation therein.
