Origin of the hot gas in low-mass protostars Herschel-PACS spectroscopy of HH 46
Journal article, 2010
Aims. "Water In Star-forming regions with Herschel" (WISH) is a Herschel key programme aimed at understanding the physical and chemical structure of young stellar objects (YSOs) with a focus on water and related species. Methods. The low-mass protostar HH 46 was observed with the Photodetector Array Camera and Spectrometer (PACS) on the Herschel Space Observatory to measure emission in H2O, CO, OH, [O I], and [C II] lines located between 63 and 186 mu m. The excitation and spatial distribution of emission can disentangle the different heating mechanisms of YSOs, with better spatial resolution and sensitivity than previously possible. Results. Far-IR line emission is detected at the position of the protostar and along the outflow axis. The OH emission is concentrated at the central position, CO emission is bright at the central position and along the outflow, and H2O emission is concentrated in the outflow. In addition, [O I] emission is seen in low-velocity gas, assumed to be related to the envelope, and is also seen shifted up to 170 km s(-1) in both the red-and blue-shifted jets. Envelope models are constructed based on previous observational constraints. They indicate that passive heating of a spherical envelope by the protostellar luminosity cannot explain the high-excitation molecular gas detected with PACS, including CO lines with upper levels at >2500 K above the ground state. Instead, warm CO and H2O emission is probably produced in the walls of an outflow-carved cavity in the envelope, which are heated by UV photons and non-dissociative C-type shocks. The bright OH and [O I] emission is attributed to J-type shocks in dense gas close to the protostar. In the scenario described here, the combined cooling by far-IR lines within the central spatial pixel is estimated to be 2 x 10(-2) L-circle dot, with 60-80% attributed to J- and C-type shocks produced by interactions between the jet and the envelope.
ISM: jets and
outflows
outflow
water
stars: formation
hh-46/47
ISM: molecules
shock
jets
emission
ISM: individual objects: HH 46
astrochemistry
i.
Author
T. A. van Kempen
Leiden University
Harvard-Smithsonian Center for Astrophysics
L. Kristensen
Leiden University
G. J. Herczeg
Max Planck Society
R. Visser
Leiden University
E. F. van Dishoeck
Max Planck Society
Leiden University
S. F. Wampfler
Swiss Federal Institute of Technology in Zürich (ETH)
S. Bruderer
Swiss Federal Institute of Technology in Zürich (ETH)
A. O. Benz
Swiss Federal Institute of Technology in Zürich (ETH)
S. Doty
Denison University
C. Brinch
Leiden University
M. R. Hogerheijde
Leiden University
J. K. Jorgensen
University of Copenhagen
M. Tafalla
Spanish National Observatory (OAN)
D. A. Neufeld
Johns Hopkins University
R. Bachiller
Spanish National Observatory (OAN)
A. Baudry
Laboratoire d'Astrophysique de Bordeaux
M. Benedettini
Istituto di Fisica dello Spazio Interplanetario, Rome
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
P. Caselli
Arcetri Astrophysical Observatory
University of Leeds
J. Cernicharo
Centro de Astrobiologia (CAB)
C. Codella
Arcetri Astrophysical Observatory
F. Daniel
Centro de Astrobiologia (CAB)
A. M. di Giorgio
Istituto di Fisica dello Spazio Interplanetario, Rome
C. Dominik
Anton Pannekoek Institute for Astronomy
Radboud University
P. Encrenaz
LERMA - Laboratoire d'Etudes du Rayonnement et de la Matiere en Astrophysique et Atmospheres
M. Fich
University of Waterloo
A. Fuente
Spanish National Observatory (OAN)
T. Giannini
Osservatorio Astronomico di Roma
J. R. Goicoechea
Centro de Astrobiologia (CAB)
T. de Graauw
Netherlands Institute for Space Research (SRON)
F. Helmich
Netherlands Institute for Space Research (SRON)
F. Herpin
Laboratoire d'Astrophysique de Bordeaux
T. Jacq
Laboratoire d'Astrophysique de Bordeaux
D. Johnstone
National Research Council Canada
University of Victoria
M. J. Kaufman
San Jose State University
B. Larsson
Stockholm University
D. Lis
California Institute of Technology (Caltech)
René Liseau
Chalmers, Earth and Space Sciences, Radio Astronomy and Astrophysics
M. Marseille
Netherlands Institute for Space Research (SRON)
C. McCoey
University of Waterloo
G. J. Melnick
Harvard-Smithsonian Center for Astrophysics
B. Nisini
Osservatorio Astronomico di Roma
Michael Olberg
Chalmers, Earth and Space Sciences, Onsala Space Observatory
B. Parise
Max Planck Society
J. C. Pearson
Jet Propulsion Laboratory, California Institute of Technology
R. Plume
University of Calgary
C. Risacher
Netherlands Institute for Space Research (SRON)
J. Santiago-García
Institut de Radioastronomie Millimétrique (IRAM)
P. Saraceno
Istituto di Fisica dello Spazio Interplanetario, Rome
R. Shipman
Netherlands Institute for Space Research (SRON)
F. F. S. van der Tak
Netherlands Institute for Space Research (SRON)
University of Groningen
F. Wyrowski
Max Planck Society
U. A. Yildiz
Leiden University
M. Ciechanowicz
Max Planck Society
L. Dubbeldam
Netherlands Institute for Space Research (SRON)
S. Glenz
University of Cologne
R. Huisman
Netherlands Institute for Space Research (SRON)
Robert Lin
Max Planck Society
P. Morris
California Institute of Technology (Caltech)
J. A. Murphy
Maynooth University
N. Trappe
Maynooth University
Astronomy and Astrophysics
0004-6361 (ISSN) 1432-0746 (eISSN)
Vol. 518 Article Number: L121 L121Subject Categories (SSIF 2011)
Astronomy, Astrophysics and Cosmology
DOI
10.1051/0004-6361/201014615