English (United Kingdom)

https://curated-unify.zendy.io/wp-json/zendy-region/v1/featured_content/oa?rat=en

https://curated-unify.zendy.io/wp-json/zendy-region/v1/highlighted_journal/

Global: Zendy Plus annual

Presents the access of premium content as premium feature

Premium Content

Presents the keyphrase highlighting as premium feature

Keyphrase Highlighting

Presents the summarisation as premium feature

Summarisation

Insights

Presents the pdf analysis as premium feature

PDF Analysis

Presents the zaia usage as premium feature

ZAIA

Global: Zendy Tools annual

Global: Zendy Free Plan

Global: Zendy Tools monthly

Global: Zendy Plus monthly

Measuring the water deuterium fractionation in the inner warm regions oflow-mass protostars has so far been hampered by poor angular resolutionobtainable with single-dish ground- and space-based telescopes. Observations ofwater isotopologues using (sub)millimeter wavelength interferometers have thepotential to shed light on this matter. Observations toward IRAS 16293-2422 ofthe 5(3,2)-4(4,1) transition of H2-18O at 692.07914 GHz from Atacama LargeMillimeter/submillimeter Array (ALMA) as well as the 3(1,3)-2(2,0) of H2-18O at203.40752 GHz and the 3(1,2)-2(2,1) transition of HDO at 225.89672 GHz from theSubmillimeter Array (SMA) are presented. The 692 GHz H2-18O line is seen towardboth components of the binary protostar. Toward one of the components, "sourceB", the line is seen in absorption toward the continuum, slightly red-shiftedfrom the systemic velocity, whereas emission is seen off-source at the systemicvelocity. Toward the other component, "source A", the two HDO and H2-18O linesare detected as well with the SMA. From the H2-18O transitions the excitationtemperature is estimated at 124 +/- 12 K. The calculated HDO/H2O ratio is (9.2+/- 2.6)*10^(-4) - significantly lower than previous estimates in the warm gasclose to the source. It is also lower by a factor of ~5 than the ratio deducedin the outer envelope. Our observations reveal the physical and chemicalstructure of water vapor close to the protostars on solar-system scales. Thered-shifted absorption detected toward source B is indicative of infall. Theexcitation temperature is consistent with the picture of water ice evaporationclose to the protostar. The low HDO/H2O ratio deduced here suggests that thedifferences between the inner regions of the protostars and the Earth's oceansand comets are smaller than previously thought.

Warm water deuterium fractionation in IRAS 16293-2422 - The high-resolution ALMA and SMA view