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 Plus monthly

Global: Zendy Tools annual

Global: Zendy Tools monthly

Global: Zendy Free Plan

(Abridged) We present a survey of the water emission in a sample of more than20 outflows from low mass young stellar objects with the goal of characterizingthe physical and chemical conditions of the emitting gas. We have used the HIFIand PACS instruments on board the Herschel Space Observatory to observe the twofundamental lines of ortho-water at 557 and 1670 GHz. These observations werepart of the "Water In Star-forming regions with Herschel" (WISH) key program,and have been complemented with CO and H2 data. We find that the emission fromwater has a different spatial and velocity distribution from that of the J=1-0and 2-1 transitions of CO, but it has a similar spatial distribution to H2, andits intensity follows the H2 intensity derived from IRAC images. This suggeststhat water traces the outflow gas at hundreds of kelvins responsible for the H2emission, and not the component at tens of kelvins typical of low-J COemission. A warm origin of the water emission is confirmed by a remarkablecorrelation between the intensities of the 557 and 1670 GHz lines, which alsoindicates the emitting gas has a narrow range of excitations. A non-LTEradiative transfer analysis shows that while there is some ambiguity on theexact combination of density and temperature values, the gas thermal pressurenT is constrained within less than a factor of 2. The typical nT over thesample is 4 10^{9} cm^{-3}K, which represents an increase of 10^4 with respectto the ambient value. The data also constrain within a factor of 2 the watercolumn density. When this quantity is combined with H2 column densities, thetypical water abundance is only 3 10^{-7}, with an uncertainty of a factor of3. Our data challenge current C-shock models of water production due to acombination of wing-line profiles, high gas compressions, and low abundances.

High-pressure, low-abundance water in bipolar outflows. Results from a Herschel-WISH survey