摘要
Molecular oxygen abundance is a key parameter in understanding the chemical network of the interstellar medium.We estimate the molecular oxygen column density and abundance for a sample of Galactic massive star formation regions based on observations from the Submillimiter Wave Astronomy Satellite(SWAS)survey.We obtained an averaged O_(2)spectrum based on this sample using the(SWAS)survey data(O_(2),487.249 GHz,N=3-1,J=3-2).No emission or absorption feature is seen around the supposed central velocity with a total integration time of t_(total)=8.67×10^(3)hr and an rms noise per channel of 1.45 m K.Assuming a kinetic temperature T_(kin)=30 K,we derive the 3σupper limit of the O_(2)column density to be 3.3×10^(15)cm^(-2),close to the lowest values reported in Galactic massive star formation regions in previous studies.The corresponding O_(2)abundance upper limit is6.7×10^(-8),lower than all previous results based on SWAS observations and is close to the lowest reported value in massive star formation regions.On a galactic scale,our statistical results confirm a generally low O_(2)abundance for Galactic massive star formation regions.This abundance is also lower than results reported in extragalactic sources.
基金
supported by the National Natural Science Foundation of China(NSFC,Grant Nos.11988101 and12041302)
the International Partnership Program of the Chinese Academy of Sciences(grant No.114A11KYSB20210010)
National Key R&D Program of China No.2023YFA1608004
operated by the California Institute of Technology under a contract with the National Aeronautics and Space Administration(80NM0018D0004)
the support of the Tianchi Talent Program of Xinjiang Uygur Autonomous Region
the Collaborative Research Center 1601(SFB 1601 sub-project A2)
funded by the Deutsche Forschungsgemeinschaft—500700252
support from the University of Cologne and its Global Faculty program。
