Water cooling of shocks in protostellar outflows Herschel-PACS map of L1157
Artikel i vetenskaplig tidskrift, 2010

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 mu m transition obtained toward the young outflow L1157. Methods. The 179 mu m 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 mu m emission is spatially correlated with emission from H-2 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 mu m 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 similar to 10(-1) L-circle dot, about 40% of the cooling due to H-2 and 23% of the total energy released in shocks along the L1157 outflow.

gas

ISM: molecules

ISM: jets and outflows

emission

stars: formation

swas

class-0 sources

Författare

B. Nisini

Osservatorio Astronomico di Roma

M. Benedettini

Istituto di Fisica dello Spazio Interplanetario, Rome

C. Codella

Osservatorio Astrofisico di Arcetri

T. Giannini

Osservatorio Astronomico di Roma

René Liseau

Chalmers, Rymd- och geovetenskap, Radioastronomi och astrofysik

D. A. Neufeld

Johns Hopkins University

M. Tafalla

Observatorio Astronomico Nacional

E. F. van Dishoeck

Max Planck-institutet

Leiden University

R. Bachiller

Observatorio Astronomico Nacional

A. Baudry

Laboratoire d'Astrophysique de Bordeaux

A. O. Benz

Eidgenössische Technische Hochschule Zürich (ETH)

E. A. Bergin

University of Michigan

Per Bjerkeli

Chalmers, Rymd- och geovetenskap, Radioastronomi och astrofysik

G. A. Blake

Caltech Division of Geological and Planetary Sciences

S. Bontemps

Laboratoire d'Astrophysique de Bordeaux

J. Braine

Laboratoire d'Astrophysique de Bordeaux

S. Bruderer

Eidgenössische Technische Hochschule Zürich (ETH)

P. Caselli

Osservatorio Astrofisico di Arcetri

University of Leeds

J. Cernicharo

CSIC-INTA - Centro de Astrobiologia (CAB)

F. Daniel

CSIC-INTA - Centro de Astrobiologia (CAB)

P. Encrenaz

LERMA - Laboratoire d'Etudes du Rayonnement et de la Matiere en Astrophysique et Atmospheres

A. M. di Giorgio

Istituto di Fisica dello Spazio Interplanetario, Rome

C. Dominik

Radboud Universiteit

Astronomical Institute Anton Pannekoek

S. Doty

Denison University

M. Fich

University of Waterloo

A. Fuente

Observatorio Astronomico Nacional

J. R. Goicoechea

CSIC-INTA - Centro de Astrobiologia (CAB)

T. de Graauw

SRON Netherlands Institute for Space Research

F. Helmich

SRON Netherlands Institute for Space Research

G. J. Herczeg

Max Planck-institutet

F. Herpin

Laboratoire d'Astrophysique de Bordeaux

M. Hogerheijde

Leiden University

T. Jacq

Laboratoire d'Astrophysique de Bordeaux

D. Johnstone

University of Victoria

National Research Council Canada

J. K. Jorgensen

Kobenhavns Universitet

M. Kaufman

San Jose State University

L. Kristensen

Leiden University

B. Larsson

Stockholms universitet

D. Lis

Caltech Division of Geological and Planetary Sciences

M. Marseille

SRON Netherlands Institute for Space Research

C. McCoey

University of Waterloo

G. J. Melnick

Harvard-Smithsonian Center for Astrophysics

Michael Olberg

Chalmers, Rymd- och geovetenskap, Onsala rymdobservatorium

B. Parise

Stockholms universitet

J. C. Pearson

Jet Propulsion Laboratory, California Institute of Technology

R. Plume

University of Calgary

C. Risacher

SRON Netherlands Institute for Space Research

J. Santiago

Observatorio Astronomico Nacional

P. Saraceno

Istituto di Fisica dello Spazio Interplanetario, Rome

R. Shipman

SRON Netherlands Institute for Space Research

T. A. van Kempen

Harvard-Smithsonian Center for Astrophysics

R. Visser

Leiden University

S. Viti

Istituto di Fisica dello Spazio Interplanetario, Rome

University College London (UCL)

S. F. Wampfler

Eidgenössische Technische Hochschule Zürich (ETH)

F. Wyrowski

Max Planck-institutet

F. F. S. van der Tak

University of Groningen, Kapteyn Astronomical Institute

SRON Netherlands Institute for Space Research

U. A. Yildiz

Leiden University

B. Delforge

École Normale Supérieure

Radboud Universiteit

J. Desbat

Laboratoire d'Astrophysique de Bordeaux

W. A. Hatch

University of Calgary

I. Peron

École Normale Supérieure

Radboud Universiteit

Institut de RadioAstronomie Millimetrique (IRAM)

R. Schieder

Universität zu Köln

J. A. Stern

University of Calgary

D. Teyssier

European Space Astronomy Centre

N. Whyborn

Astronomy and Astrophysics

0004-6361 (ISSN) 1432-0746 (eISSN)

Vol. 518 L120

Ämneskategorier

Astronomi, astrofysik och kosmologi

DOI

10.1051/0004-6361/201014603