Planck Cold Clumps in the lambda Orionis Complex. III. A chemical probe
  of stellar feedback on cores in the lambda Orionis cloud
  Massive stars have a strong impact on their local environments. However, how
stellar feedback regulates star formation is still under debate. In this
context, we studied the chemical properties of 80 dense cores in the Orion
molecular cloud complex composed of the Orion A (39 cores), B (26 cores), and
lambda Orionis (15 cores) clouds using multiple molecular line data taken with
the Korean Very Long Baseline Interferometry Network (KVN) 21-m telescopes. The
lambda Orionis cloud has an H ii bubble surrounding the O-type star lambda Ori,
and hence it is exposed to the ultraviolet (UV) radiation field of the massive
star. The abundances of C2H and HCN, which are sensitive to UV radiation,
appear to be higher in the cores in the lambda Orionis cloud than those in the
Orion A and B clouds, while the HDCO to H2CO abundance ratios show an opposite
trend, indicating a warmer condition in the lambda Orionis cloud. The detection
rates of dense gas tracers such as the N2H+, HCO+, and H13CO+ lines are also
lower in the lambda Orionis cloud. These chemical properties imply that the
cores in the lambda Orionis cloud are heated by UV photons from lambda Ori.
Furthermore, the cores in the lambda Orionis cloud do not show any
statistically significant excess in the infall signature of HCO+ (1 - 0),
unlike the Orion A and B clouds. Our results support the idea that feedback
from massive stars impacts star formation in a negative way by heating and
evaporating dense materials, as in the lambda Orionis cloud.
