摘要
In this work,we perform a statistical investigation towards 50 high-mass clumps using data from the Bolocam Galactic Plane Survey（BGPS）and Millimetre Astronomy Legacy Team 90-GHz survey（MALT90）.Eleven dense molecular lines（N2H^＋（1–0）,HNC（1–0）,HCO^＋（1–0）,HCN（1–0）,HN^（13）C（1–0）,H^（13）CO^＋（1–0）,C2H（1–0）,HC3N（10–9）,SiO（2–1）,^（13）CS（2–1）and HNCO（4（4,0）-3（0,3）））are detected.N2H^＋ and HNC are shown to be good tracers for clumps in various evolutionary stages since they are detected in all the fields.The detection rates of N-bearing molecules decrease as the clumps evolve,but those of O-bearing species increase with evolution.Furthermore,the abundance ratios[N2H^＋]/[HCO^＋]and log（[HC3N]/[HCO^＋]）decline with log（[HCO^＋]）as two linear functions,respectively.This suggests that N^＋2H^＋ and HC3N transform to HCOas the clumps evolve.We also find that C2H is the most abundant molecule with an order of magnitude 10^（-8）.In addition,three new infall candidates,G010.214–00.324,G011.121–00.128 and G012.215–00.118（a）,are discovered to have large-scale infall motions and infall rates with an order of magnitude 10^（-3）M⊙yr^（-1）.
In this work,we perform a statistical investigation towards 50 high-mass clumps using data from the Bolocam Galactic Plane Survey（BGPS）and Millimetre Astronomy Legacy Team 90-GHz survey（MALT90）.Eleven dense molecular lines（N2H^＋（1–0）,HNC（1–0）,HCO^＋（1–0）,HCN（1–0）,HN^（13）C（1–0）,H^（13）CO^＋（1–0）,C2H（1–0）,HC3N（10–9）,SiO（2–1）,^（13）CS（2–1）and HNCO（4（4,0）-3（0,3）））are detected.N2H^＋ and HNC are shown to be good tracers for clumps in various evolutionary stages since they are detected in all the fields.The detection rates of N-bearing molecules decrease as the clumps evolve,but those of O-bearing species increase with evolution.Furthermore,the abundance ratios[N2H^＋]/[HCO^＋]and log（[HC3N]/[HCO^＋]）decline with log（[HCO^＋]）as two linear functions,respectively.This suggests that N^＋2H^＋ and HC3N transform to HCOas the clumps evolve.We also find that C2H is the most abundant molecule with an order of magnitude 10^（-8）.In addition,three new infall candidates,G010.214–00.324,G011.121–00.128 and G012.215–00.118（a）,are discovered to have large-scale infall motions and infall rates with an order of magnitude 10^（-3）M⊙yr^（-1）.
基金
supported by the National Natural Science Foundation of China(Nos.11363004 and 11403042)
supported by the National Key Basic Research Program of China(No.2015CB857100)
