DNC/HNC RATIO OF MASSIVE CLUMPS IN EARLY EVOLUTIONARY STAGES OF HIGH-MASS STAR FORMATION
DNC/HNC RATIO OF MASSIVE CLUMPS IN EARLY EVOLUTIONARY STAGES OF HIGH-MASS STAR FORMATION
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DOI：
10.1088/0004-637x/747/2/140
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发表时间：
2012-01
期刊：
影响因子：
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通讯作者：
T. Sakai;N. Sakai;K. Furuya;Y. Aikawa;T. Hirota;S. Yamamoto
中科院分区：
文献类型：
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作者：
T. Sakai;N. Sakai;K. Furuya;Y. Aikawa;T. Hirota;S. Yamamoto
我们用Nobeama射电天文台45米望远镜观测到了包括红外暗云(IRDC)和大质量原恒星天体(HMPO)在内的18个质量团的HN13C J=1-0和DNC J=1-0谱线。我们发现，在所有观测到的源上，HN13C的发射都比DNC的发射强。对于观测到的高质量源，dnc/hnc的平均比值(0.009±0.005)确实低于低质量无星核和恒星形成核。由NH3(J，K)=(1，1)和(2，2)谱线强度得出的动力学温度在观测到的高质量源区高于低质量核区。然而，一些涉及斯皮策24μm源的红外DC的dnc/hnc比却低于hmpos，尽管IRDC的动力学温度低于hmpos。这意味着DNC/HNC的比率不仅取决于当前的动力学温度。借助于化学模型模拟，我们讨论了原恒星诞生后DNC/HNC比率如何降低。我们认为，恒星形成核中DNC/HNC的比值取决于其无星核阶段的物理条件和历史，如持续时间和气体动力学温度。
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 of the observed sources. The averaged DNC/HNC ratio is indeed lower toward the observed high-mass sources (0.009 ± 0.005) 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 μm 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.