EPoS Contribution
EPoS Contribution
Deuterated water in low-mass protostars

Audrey Coutens
Institut de Recherche en Astrophysique et Planetologie, Toulouse, France
Observations of deuterated water are an important complement for studies of H2O, since they give strong constraints on the formation processes (grain surfaces versus gas-phase chemistry) and because of its link with the comets and the Earth's oceans. The CHESS (Chemical HErschel Surveys of Star forming regions) Key Program has allowed to detect a lot of transitions of HDO and H2O as well as its isotopes H2-18O and H2-17O towards the low-mass protostar IRAS16293-2422 thanks to the unbiaised spectral survey carried out with the HIFI instrument on board the Herschel Space Observatory. Complementary data of HDO from the ground-based telescopes IRAM and JCMT are also available. In total, 13 HDO lines have been detected towards IRAS16293-2422. It is the first time that so many HDO lines are detected towards a same source, allowing a precise determination of the abundance of deuterated water through the protostar envelope. To reproduce the observed line profiles, we have performed a modeling of HDO from the hot corino to the surrounding envelope using the physical structure of the protostar and the spherical non-LTE Monte-Carlo radiative transfer code RATRAN, which takes also radiative pumping by continuum emission from dust into account. The same method has been applied to model the water isotopes H2-18O and H2-17O. We will show the results of this analysis and discuss the determined HDO/H2O ratio. We will also present a comparison with other low-mass protostars such as NGC1333-IRAS4A and IRAS4B, for which new HDO data have recently been observed.
C. Vastel, IRAP, France
E. Caux, IRAP, France
Key publication