首页|Possible Habitats for NH3,NH2D,H13CN,HC15N,SO,and C18O in the Initial Conditions of High-mass Star Formation
Possible Habitats for NH3,NH2D,H13CN,HC15N,SO,and C18O in the Initial Conditions of High-mass Star Formation
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The initial condition of high-mass star formation is a complex area of study because of the high densities(nH2＞106 cm-3)and low temperatures(Tdust＜18 K)involved.Under such conditions,many molecules become depleted from the gas phase by freezing out onto dust grains.However,the N-bearing and deuterated species could remain gaseous under these extreme conditions,suggesting that they may serve as ideal tracers.In this paper,using the Plateau de Bure Interferometer and Very Large Array observations at 1.3 mm,3.5 mm,and l.3 cm,we investigate the possible habitats for NH3,NH2D,H13CN,HC15N,SO,and C18O in eight massive precluster and protocluster clumps G18.17,G18.21,G23.97N,G23.98,G23.44,G23.97S,G25.38,and G25.71.We found that the NH3 cores are in good agreement with the 3.5 mm peak emission,but the NH3 is much more extended than the 3.5 mm emission structure.The SO distributions agree well with the 3.5 mm peaks for the evolved star formation stage,but we did not detect any SO emission in the four earliest star formation sources.C18O is a poor tracer in conditions of the cold((≲)18K)and dense((≲)104cm-3)cores,e.g.,the prestellar cores.We also found that the NH2D cores are mainly located in the temperature range of 13.0-20.0 K,and the NH2D lines may be strongly depleted above 20 K.
National Astronomical Observatories,Chinese Academy of Sciences,Beijing 100101,China
University of Chinese Academy of Sciences Beijing 100049 China
College of Science,Qiqihar University,Qiqihar 161006,China
Guizhou Radio Astronomical Observatory,Guizhou University,Guiyang 550000,China
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National Key R&D Program of Chinalocal Science and Technology innovation projects of the central governmentNational Natural Science Foundation of China(NSFC)
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