Change search
ReferencesLink to record
Permanent link

Direct link
Water cooling of shocks in protostellar outflows. Herschel-PACS map of L1157
Show others and affiliations
2010 (English)In: Astronomy and Astrophysics, ISSN 0004-6361, E-ISSN 1432-0746, Vol. 518, L120- p.Article in journal (Refereed) Published
Abstract [en]

Context. The far-IR/sub-mm spectral mapping facility provided by the Herschel-PACS and HIFI instruments has made it possible to obtain, for the first time, images of H2O emission with a spatial resolution comparable to ground based mm/sub-mm observations. Aims: In the framework of the Water In Star-forming regions with Herschel (WISH) key program, maps in water lines of several outflows from young stars are being obtained, to study the water production in shocks and its role in the outflow cooling. This paper reports the first results of this program, presenting a PACS map of the o-H2O 179 μm transition obtained toward the young outflow L1157. Methods: The 179 μm map is compared with those of other important shock tracers, and with previous single-pointing ISO, SWAS, and Odin water observations of the same source that allow us to constrain the H2O abundance and total cooling. Results: Strong H2O peaks are localized on both shocked emission knots and the central source position. The H2O 179 μm emission is spatially correlated with emission from H2 rotational lines, excited in shocks leading to a significant enhancement of the water abundance. Water emission peaks along the outflow also correlate with peaks of other shock-produced molecular species, such as SiO and NH3. A strong H2O peak is also observed at the location of the proto-star, where none of the other molecules have significant emission. The absolute 179 μm intensity and its intensity ratio to the H2O 557 GHz line previously observed with Odin/SWAS indicate that the water emission originates in warm compact clumps, spatially unresolved by PACS, having a H2O abundance of the order of 10-4. This testifies that the clumps have been heated for a time long enough to allow the conversion of almost all the available gas-phase oxygen into water. The total H2O cooling is ~10-1 L_ȯ, about 40% of the cooling due to H2 and 23% of the total energy released in shocks along the L1157 outflow. Herschel is an ESA space observatory with science instruments provided by European-led Principal Investigator consortia and with important partecipation from NASA.

Place, publisher, year, edition, pages
2010. Vol. 518, L120- p.
Keyword [en]
stars: formation, ISM: jets and outflows, ISM: molecules
National Category
Astronomy, Astrophysics and Cosmology
Research subject
URN: urn:nbn:se:su:diva-51504DOI: 10.1051/0004-6361/201014603ISI: 000281527200121OAI: diva2:384627
authorCount :65Available from: 2011-01-10 Created: 2011-01-10 Last updated: 2011-01-11Bibliographically approved

Open Access in DiVA

No full text

Other links

Publisher's full text

Search in DiVA

By author/editor
Larsson, Bengt
By organisation
Department of Astronomy
In the same journal
Astronomy and Astrophysics
Astronomy, Astrophysics and Cosmology

Search outside of DiVA

GoogleGoogle Scholar
The number of downloads is the sum of all downloads of full texts. It may include eg previous versions that are now no longer available

Altmetric score

Total: 30 hits
ReferencesLink to record
Permanent link

Direct link