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 Tools annual

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 monthly

Global: Zendy Plus monthly

Presents the access of premium content as premium feature

Premium Content

Global: Zendy Plus annual

Global: Zendy Free Plan

Our present understanding of high-mass star formation still remains veryschematic. In particular, it is not yet clear how much of the differencebetween low-mass and high-mass star formation occurs during the earliest starformation phases. The chemical characteristics of massive cold clumps, and thecomparison with those of their low-mass counterparts, could provide crucialclues about the exact role that chemistry plays in differentiating the earlyphases of low-mass and high-mass star formation. Water, in particular, is aunique probe of physical and chemical conditions in star-forming regions. Usingthe HIFI instrument of Herschel we have observed the ortho-NH3 (1_0-0_0)(572GHz), ortho-H2O (1_10-1_01) (557GHz) and N2H+ (6-5) (559GHz) lines toward asample of high-mass starless and proto-stellar clumps selected from the"Herschel} Infrared Galactic Plane Survey" (Hi-GAL). We compare our results toprevious studies of low-mass and high-mass proto-stellar objects. At least oneof the three molecular lines was detected in 4 (out of 35) and 7 (out of 17)objects in the l=59deg and l=30deg galactic regions, respectively. All detectedsources are proto-stellar. The water spectra are complex and consist of severalkinematic components, identified through a Gaussian decomposition, and in a fewsources inverse and regular P-Cygni profiles have been detected. All water lineprofiles of the l=59deg region are dominated by a broad Gaussian emissionfeature, indicating that the bulk of the water emission arises in outflows. Nosuch broad emission is detected toward the l=30deg objects. The ammonia line insome cases also shows line wings and an inverse P-Cygni profile, thusconfirming that NH3 rotational transitions can be used to probe the dynamics ofhigh-mass star forming regions. Both bolometric and water line luminosityincrease with the continuum temperature.

Herschel-HIFI observations of H2O, NH3 and N2H+ toward high-mass starless and proto-stellar clumps identified by the Hi-GAL survey