Water cooling of shocks in protostellar outflows Herschel-PACS map of L1157
Journal article, 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.
stars: formation
gas
ISM: molecules
emission
class-0 sources
ISM: jets and outflows
swas
Author
B. Nisini
Osservatorio Astronomico di Roma
M. Benedettini
Istituto di Fisica dello Spazio Interplanetario, Rome
C. Codella
Arcetri Astrophysical Observatory
T. Giannini
Osservatorio Astronomico di Roma
René Liseau
Chalmers, Earth and Space Sciences, Radio Astronomy and Astrophysics
D. A. Neufeld
Johns Hopkins University
M. Tafalla
Spanish National Observatory (OAN)
E. F. van Dishoeck
Max Planck Society
Leiden University
R. Bachiller
Spanish National Observatory (OAN)
A. Baudry
Laboratoire d'Astrophysique de Bordeaux
A. O. Benz
Swiss Federal Institute of Technology in Zürich (ETH)
E. A. Bergin
University of Michigan
Per Bjerkeli
Chalmers, Earth and Space Sciences, Radio Astronomy and Astrophysics
G. A. Blake
California Institute of Technology (Caltech)
S. Bontemps
Laboratoire d'Astrophysique de Bordeaux
J. Braine
Laboratoire d'Astrophysique de Bordeaux
S. Bruderer
Swiss Federal Institute of Technology in Zürich (ETH)
P. Caselli
University of Leeds
Arcetri Astrophysical Observatory
J. Cernicharo
Centro de Astrobiologia (CAB)
F. Daniel
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
Anton Pannekoek Institute for Astronomy
Radboud University
S. Doty
Denison University
M. Fich
University of Waterloo
A. Fuente
Spanish National Observatory (OAN)
J. R. Goicoechea
Centro de Astrobiologia (CAB)
T. de Graauw
Netherlands Institute for Space Research (SRON)
F. Helmich
Netherlands Institute for Space Research (SRON)
G. J. Herczeg
Max Planck Society
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
University of Copenhagen
M. Kaufman
San Jose State University
L. Kristensen
Leiden University
B. Larsson
Stockholm University
D. Lis
California Institute of Technology (Caltech)
M. Marseille
Netherlands Institute for Space Research (SRON)
C. McCoey
University of Waterloo
G. J. Melnick
Harvard-Smithsonian Center for Astrophysics
Michael Olberg
Chalmers, Earth and Space Sciences, Onsala Space Observatory
B. Parise
Stockholm University
J. C. Pearson
California Institute of Technology (Caltech)
R. Plume
University of Calgary
C. Risacher
Netherlands Institute for Space Research (SRON)
J. Santiago
Spanish National Observatory (OAN)
P. Saraceno
Istituto di Fisica dello Spazio Interplanetario, Rome
R. Shipman
Netherlands Institute for Space Research (SRON)
T. A. van Kempen
Harvard-Smithsonian Center for Astrophysics
R. Visser
Leiden University
S. Viti
University College London (UCL)
Istituto di Fisica dello Spazio Interplanetario, Rome
S. F. Wampfler
Swiss Federal Institute of Technology in Zürich (ETH)
F. Wyrowski
Max Planck Society
F. F. S. van der Tak
Netherlands Institute for Space Research (SRON)
University of Groningen
U. A. Yildiz
Leiden University
B. Delforge
Radboud University
Ecole Normale Superieure (ENS)
J. Desbat
Laboratoire d'Astrophysique de Bordeaux
W. A. Hatch
University of Calgary
I. Peron
Radboud University
Institut de Radioastronomie Millimétrique (IRAM)
Ecole Normale Superieure (ENS)
R. Schieder
University of Cologne
J. A. Stern
University of Calgary
D. Teyssier
European Space Agency (ESA)
N. Whyborn
Astronomy and Astrophysics
0004-6361 (ISSN) 1432-0746 (eISSN)
Vol. 518 Article Number: L120 L120Subject Categories (SSIF 2011)
Astronomy, Astrophysics and Cosmology
DOI
10.1051/0004-6361/201014603