The HDO/H2O Ratio in Gas in the Inner Regions of a Low-mass Protostar
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The HDO/H2O abundance ratio is thought to be a key diagnostic
for the evolution of water during the star and planet formation process
and thus for its origin on Earth. We here present millimeter-wavelength
high angular resolution observations of the deeply embedded protostar
NGC 1333-IRAS4B from the Submillimeter Array targeting the
312-221 transition of HDO at 225.6 GHz
(Eu = 170 K). We do not (or only very tentatively) detect the
HDO line toward the central protostar, contrasting the previous
prominent detection of a line from another water isotopologue,
H18 2O, with similar excitation properties using
the IRAM Plateau de Bure Interferometer. The non-detection of the HDO
line provides a direct, model-independent, upper limit to the
HDO/H2O abundance ratio of 6 × 10-4
(3s) in the warm gas associated with the central protostar. This
upper limit suggests that the HDO/H2O abundance ratio is not
significantly enhanced in the inner ˜50 AU around the protostar
relative to what is seen in comets and Earth's oceans and does not
support previous suggestions of a generally enhanced HDO/H2O
ratio in these systems.
Original language | English |
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Journal | Astrophysics Journal Letters |
Volume | 725 |
Issue number | 2 |
Pages (from-to) | 172 |
ISSN | 2041-8205 |
DOIs | |
Publication status | Published - 1 Dec 2010 |
ID: 35114119