Journal
ASTRONOMY & ASTROPHYSICS
Volume 521, Issue -, Pages -Publisher
EDP SCIENCES S A
DOI: 10.1051/0004-6361/201015101
Keywords
astrochemistry; ISM: molecules; submillimeter: ISM; ISM: abundances; molecular processes; line: identification
Categories
Funding
- Science and Technology Facilities Council [ST/F002092/1, ST/F501761/1] Funding Source: researchfish
- STFC [ST/F501761/1, ST/F002092/1] Funding Source: UKRI
Ask authors/readers for more resources
Context. Despite the low elemental deuterium abundance in the Galaxy, enhanced molecular D/H ratios have been found in the environments of low-mass star-forming regions, and in particular the Class 0 protostar IRAS 16293-2422. Aims. The CHESS (Chemical HErschel Surveys of Star forming regions) key program aims to study the molecular complexity of the interstellar medium. The high sensitivity and spectral resolution of the Herschel/HIFI instrument provide a unique opportunity to observe the fundamental 1(1,1)-0(0,0) transition of the ortho-D2O molecule, which is inaccessible from the ground, and determine the ortho-to-para D2O ratio. Methods. We detected the fundamental transition of the ortho-D2O molecule at 607.35 GHz towards IRAS 16293-2422. The line is seen in absorption with a line opacity of 0.62 +/- 0.11 (1 sigma). From the previous ground-based observations of the fundamental 1(1,0)-1(0,1) transition of para-D2O seen in absorption at 316.80 GHz, we estimate a line opacity of 0.26 +/- 0.05 (1 sigma). Results. We show that the observed absorption is caused by the cold gas in the envelope of the protostar. Using these new observations, we estimate for the first time the ortho-to-para D2O ratio to be lower than 2.6 at a 3 sigma level of uncertainty, which should be compared with the thermal equilibrium value of 2:1.
Authors
I am an author on this paper
Click your name to claim this paper and add it to your profile.
Reviews
Recommended
No Data Available