Herschel observations of ortho- and para-oxidaniumyl (H2O+) in spiral arm clouds toward Sagittarius?B2(M)

摘要

H2O+ has been observed inits ortho- and para- statestoward the massive star forming core SgrB2(M),located close to the Galactic center. The observations show absorptionin all spiral arm clouds between the Sun and SgrB2. Theaverage o/p ratio of H2O+in most velocity intervals is4.8, which corresponds to anuclear spin temperature of 21K. The relationship of thisspin temperature to the formation temperature and current physicaltemperature of the gas hosting H2O+is discussed, but no firm conclusion is reached. In the velocityinterval 0-60kms-1, an ortho/pararatio of below unity is found, but if this is due to an artifact ofcontamination by other species or real is not clear.Key words: astrochemistry - line: profiles- molecular processes