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Water in low-mass star-forming regions with Herschel . HIFI spectroscopy of NGC 1333
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2010 (English)In: Astronomy and Astrophysics, ISSN 0004-6361, E-ISSN 1432-0746, Vol. 521, L30- p.Article in journal (Refereed) Published
Abstract [en]

“Water In Star-forming regions with Herschel” (WISH) is a key programme dedicated to studying the role of water and related species during the star-formation process and constraining the physical and chemical properties of young stellar objects. The Heterodyne Instrument for the Far-Infrared (HIFI) on the Herschel Space Observatory observed three deeply embedded protostars in the low-mass star-forming region NGC 1333 in several H_216O, H_218O, and CO transitions. Line profiles are resolved for five H_216O transitions in each source, revealing them to be surprisingly complex. The line profiles are decomposed into broad (>20 km s-1), medium-broad (~5-10 km s-1), and narrow (<5 km s-1) components. The H_218O emission is only detected in broad 110-101 lines (>20 km s-1), indicating that its physical origin is the same as for the broad H_216O component. In one of the sources, IRAS4A, an inverse P Cygni profile is observed, a clear sign of infall in the envelope. From the line profiles alone, it is clear that the bulk of emission arises from shocks, both on small (⪉1000 AU) and large scales along the outflow cavity walls (~10 000 AU). The H2O line profiles are compared to CO line profiles to constrain the H2O abundance as a function of velocity within these shocked regions. The H2O/CO abundance ratios are measured to be in the range of ~0.1-1, corresponding to H2O abundances of ~10-5-10-4 with respect to H2. Approximately 5-10% of the gas is hot enough for all oxygen to be driven into water in warm post-shock gas, mostly at high velocities. Herschel is an ESA space observatory with science instruments provided by European-led Principal Investigator consortia and with important participation from NASA.Tables 2 and 3 (page 6) are only available in electronic form at

Place, publisher, year, edition, pages
2010. Vol. 521, L30- p.
Keyword [en]
astrochemistry, stars: formation, ISM: molecules, ISM: jets and outflows, ISM: individual objects: NGC 1333
National Category
Astronomy, Astrophysics and Cosmology
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URN: urn:nbn:se:su:diva-51501DOI: 10.1051/0004-6361/201015100ISI: 000284150900030OAI: diva2:384654
authorCount :67Available from: 2011-01-10 Created: 2011-01-10 Last updated: 2011-01-10Bibliographically approved

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Larsson, Bengt
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