In search of infall motion in molecular clumps II: HCO+ (1–0) and HCN (1–0) observations toward a sub-sample of infall candidates
In search of infall motion in molecular clumps II: HCO+ (1–0) and HCN (1–0) observations toward a sub-sample of infall candidates
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DOI：
10.1088/1674-4527/20/8/115
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发表时间：
2020-03
影响因子：
1.8
通讯作者：
Y. Yang 杨;Zhi-Bo 治波 Jiang 汀;Z. Chen 陈;S. Zhang 张;S. Yu 于;Yi-Ping 一平 Ao 敖
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作者：
Y. Yang 杨;Zhi-Bo 治波 Jiang 汀;Z. Chen 陈;S. Zhang 张;S. Yu 于;Yi-Ping 一平 Ao 敖
引力吸积使原始质量累积起来。这个过程对于我们理解星星形成的初始阶段至关重要。利用光学粗线和细线的特定下沉轮廓，我们在以前的工作中从银河成像卷轴画（MWISP）CO数据中搜索具有下沉运动的团块。在本研究中，我们选择了133个来源作为一个子样本进行进一步的研究和识别。这些源的激发温度在7.0和38.5 K之间，而H2柱密度在1021和1023 cm−2之间。我们用DLH 13.7-m望远镜观测了HCO ~+（1-0）和HCN（1-0）光学粗线，在这两条粗线中发现了56个蓝色轮廓而无红色轮廓的可能有着入轨运动的源，探测率为42%。这表明，利用CO数据来限制样本可以有效地提高入轨检测率。在这些确认的陨石坑源中，有43个与0/I类年轻恒星天体（YSO）有关，13个不是。这13个来源可能与早期演化阶段的来源有关。相比之下，与0/I类YSO相关的确认源具有较高的激发温度和柱密度，而其他源温度较低，柱密度较低。我们确认的大多数源的下落速度在10 - 1到100 km s-1之间，这与以前的研究一致。
Gravitational accretion accumulates the original mass. This process is crucial for us to understand the initial phases of star formation. Using the specific infall profiles in optically thick and thin lines, we searched the clumps with infall motion from the Milky Way Imaging Scroll Painting (MWISP) CO data in previous work. In this study, we selected 133 sources as a sub-sample for further research and identification. The excitation temperatures of these sources are between 7.0 and 38.5 K, while the H2 column densities are between 1021 and 1023 cm−2. We have observed optically thick lines HCO+ (1–0) and HCN (1–0) using the DLH 13.7-m telescope, and found 56 sources with a blue profile and no red profile in these two lines, which are likely to have infall motions, with a detection rate of 42%. This suggests that using CO data to restrict the sample can effectively improve the infall detection rate. Among these confirmed infall sources are 43 associated with Class 0/I young stellar objects (YSOs), and 13 which are not. These 13 sources are probably associated with the sources in the earlier evolutionary stage. In comparison, the confirmed sources that are associated with Class 0/I YSOs have higher excitation temperatures and column densities, while the other sources are colder and have lower column densities. Most infall velocities of the sources that we confirmed are between 10−1 to 100 km s−1, which is consistent with previous studies.