Publication Date
2010
Journal or Book Title
Astronomy and Astrophysics
Abstract
We present Herschel/HIFI observations of the fundamental rotational transitions of ortho- and para-H216O and H218O in absorption towards Sagittarius B2(M) and W31C. The ortho/para ratio in water in the foreground clouds on the line of sight towards these bright continuum sources is generally consistent with the statistical high-temperature ratio of 3, within the observational uncertainties. However, somewhat unexpectedly, we derive a low ortho/para ratio of 2.35 ± 0.35, corresponding to a spin temperature of ~27 K, towards Sagittarius B2(M) at velocities of the expanding molecular ring. Water molecules in this region appear to have formed with, or relaxed to, an ortho/para ratio close to the value corresponding to the local temperature of the gas and dust.
DOI
https://doi.org/10.1051/0004-6361/201015072
Volume
521
Issue
L26
Recommended Citation
Lis, DC; Erickson, NR; and et. al., "Herschel/HIFI measurements of the ortho/para ratio in water towards Sagittarius B2(M) and W31C*" (2010). Astronomy and Astrophysics. 1162.
https://doi.org/10.1051/0004-6361/201015072