Water abundance variations around high-mass protostars: HIFI observations of the DR21 region
2010 (English)In: Astronomy and Astrophysics, ISSN 0004-6361, E-ISSN 1432-0746, Vol. 518, L107- p.Article in journal (Refereed) Published
Context. Water is a key molecule in the star formation process, but its spatial distribution in star-forming regions is not well known. Aims: We study the distribution of dust continuum and H2O and 13CO line emission in DR21, a luminous star-forming region with a powerful outflow and a compact H ii region. Methods: Herschel-HIFI spectra near 1100 GHz show narrow 13CO 10-9 emission and H2O 111-000 absorption from the dense core and broad emission from the outflow in both lines. The H2O line also shows absorption by a foreground cloud known from ground-based observations of low-J CO lines. Results: The dust continuum emission is extended over 36” FWHM, while the 13CO and H2O lines are confined to ≈24” or less. The foreground absorption appears to peak further North than the other components. Radiative transfer models indicate very low abundances of ~2×10-10 for H2O and ~8×10-7 for 13CO in the dense core, and higher H2O abundances of ~4×10-9 in the foreground cloud and ~7×10-7 in the outflow. Conclusions: The high H2O abundance in the warm outflow is probably due to the evaporation of water-rich icy grain mantles, while the H2O abundance is kept down by freeze-out in the dense core and by photodissociation in the foreground cloud. Herschel is an ESA space observatory with science instruments provided by European-led Principal Investigator consortia and with important participation from NASA.
Place, publisher, year, edition, pages
2010. Vol. 518, L107- p.
ISM: molecules, stars: formation, astrochemistry, ISM: individual objects: DR21
Astronomy, Astrophysics and Cosmology
Research subject Astronomy
IdentifiersURN: urn:nbn:se:su:diva-51507DOI: 10.1051/0004-6361/201014515ISI: 000281527200108OAI: oai:DiVA.org:su-51507DiVA: diva2:384621
authorCount :592011-01-102011-01-102011-01-11Bibliographically approved