Takeshi Sakai, Nami Sakai, Kenji Furuya, Yuri Aikawa, Tomoya Hirota, Satoshi Yamamoto
We have observed the HN13C J=1-0 and DNC J=1-0 lines toward 18 massive
clumps, including infrared dark clouds (IRDCs) and high-mass protostellar
objects (HMPOs), by using the Nobeyama Radio Observatory 45 m telescope. We
have found that the HN13C emission is stronger than the DNC emission toward all
the observed sources. The averaged DNC/HNC ratio is indeed lower toward the
observed high-mass sources (0.009\pm0.005) than toward the low-mass starless
and star-forming cores (0.06). The kinetic temperature derived from the NH3 (J,
K) = (1, 1) and (2, 2) line intensities is higher toward the observed high-mass
sources than toward the low-mass cores. However the DNC/HNC ratio of some IRDCs
involving the Spitzer 24 {\mu}m sources is found to be lower than that of
HMPOs, although the kinetic temperature of the IRDCs is lower than that of the
HMPOs. This implies that the DNC/HNC ratio does not depend only on the current
kinetic temperature. With the aid of chemical model simulations, we discuss how
the DNC/HNC ratio decreases after the birth of protostars. We suggest that the
DNC/HNC ratio in star-forming cores depends on the physical conditions and
history in their starless-core phase, such as its duration time and the gas
kinetic temperature.
View original:
http://arxiv.org/abs/1201.4430
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