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

The HDO/H2O ratio is a powerful diagnostic to understand the evolution ofwater from the first stages of star formation to the formation of planets andcomets. Our aim is to determine precisely the abundance distribution of HDOtowards the low-mass protostar IRAS16293-2422 and learn more about the waterformation mechanisms by determining the HDO/H2O abundance ratio. A spectralsurvey of the source IRAS16293-2422 was carried out in the framework of theCHESS Herschel Key program with the HIFI instrument, allowing the detection ofnumerous HDO lines. Other transitions have been observed previously withground-based telescopes. The spherical Monte Carlo radiative transfer codeRATRAN was used to reproduce the observed line profiles of HDO by assuming anabundance jump. To determine the H2O abundance throughout the envelope, asimilar study was made of the H2-18O observed lines, as the H2O main isotopelines are contaminated by the outflows. We derive an inner HDO abundance of1.7e-7 and an outer HDO abundance of 8e-11. To reproduce the HDO absorptionlines, it is necessary to add an absorbing layer in front of the envelope. Itmay correspond to a water-rich layer created by the photodesorption of the icesat the edges of the molecular cloud. The HDO/H2O ratio is ~1.4-5.8% in the hotcorino whereas it is ~0.2-2.2% in the outer envelope. It is estimated at ~4.8%in the added absorbing layer. Although it is clearly higher than the cosmic D/Habundance, the HDO/H2O ratio remains lower than the D/H ratio derived for otherdeuterated molecules observed in the same source. The similarity of the ratiosderived in the hot corino and in the added absorbing layer suggests that waterformed before the gravitational collapse of the protostar, contrary toformaldehyde and methanol, which formed later once the CO molecules haddepleted on the grains.

A study of deuterated water in the low-mass protostar IRAS16293-2422