Herschel-HIFI measurements of the ortho-para ratio in water towards Sagittarius B2M and W31C - Astrophysics > Astrophysics of GalaxiesReportar como inadecuado




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Abstract: We present Herschel-HIFI observations of the fundamental rotationaltransitions of ortho- and para-H$ 2^{16}$O and H$ 2^{18}$O in absorptiontowards Sagittarius~B2M and W31C. The ortho-para ratio in water in theforeground clouds on the line of sight towards these bright continuum sourcesis generally consistent with the statistical high-temperature ratio of 3,within the observational uncertainties. However, somewhat unexpectedly, wederive a low ortho-para ratio of $2.35 \pm 0.35$, corresponding to a spintemperature of $\sim$27~K, towards Sagittarius~B2M at velocities of theexpanding molecular ring. Water molecules in this region appear to have formedwith, or relaxed to, an ortho-para ratio close to the value corresponding tothe local temperature of the gas and dust.



Autor: D. C. Lis, T. G. Phillips, P. F. Goldsmith, D. A. Neufeld, E. Herbst, C. Comito, P. Schilke, H. S. P. Müller, E. A. Bergin, M. G

Fuente: https://arxiv.org/







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