In search of infall motion in molecular clumpsⅡ:HCO+(1-0)and HCN(1-0)observations toward a sub-sample of infall candidates  

作　　者：Yang Yang Zhi-Bo Jiang Zhi-Wei Chen Shao-Bo Zhang Shu-Ling Yu Yi-Ping Ao 杨旸;江治波;陈志维;张少博;于书岭;敖一平(Purple Mountain Observatory,Chinese Academy of Sciences,Nanjing 210008,China;University of Science and Technology of China,Chinese Academy of Sciences,Hefei 230026,China;Center astronomy and Space Sciences,China Three Gorges University,Yichang 443002,China)

机构地区：[1]Purple Mountain Observatory,Chinese Academy of Sciences,Nanjing 210008,China [2]University of Science and Technology of China,Chinese Academy of Sciences,Hefei 230026,China [3]Center astronomy and Space Sciences,China Three Gorges University,Yichang 443002,China

出　　处：《Research in Astronomy and Astrophysics》2020年第8期129-142,共14页天文和天体物理学研究（英文版）

基　　金：the National Key R&D Program of China(Grant No.2017YFA0402702);the National Natural Science Foundation of China(NSFC,Grant Nos.10873037,11873093,11803091 and 11933011);the National Key R&D Program of China(Grant No.2017YFA0402700);the Key Research Program of Frontier Sciences,CAS(Grant No.QYZDJ-SSWSLH047)。

摘　　要：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 10^21 and 10^23 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 O/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 O/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 10^0 km s^-1,which is consistent with previous studies.

关 键 词：stars:formation ISM:kinematics and dynamics ISM:molecules radio lines:ISM 

分 类 号：P152[天文地球—天文学]