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.

stars: formation

ISM: individual objects: HH 46

emission

astrochemistry

i.

shock

ISM: jets and

outflow

jets

water

hh-46/47

ISM: molecules

outflows

Author

T. A. van Kempen

Harvard-Smithsonian Center for Astrophysics

Leiden University

L. Kristensen

Leiden University

G. J. Herczeg

Max Planck Institute

R. Visser

Leiden University

E. F. van Dishoeck

Max Planck Institute

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

Köbenhavns Universitet

M. Tafalla

Observatorio Astronomico Nacional

D. A. Neufeld

Johns Hopkins University

R. Bachiller

Observatorio Astronomico Nacional

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

Caltech Division of Geological and Planetary Sciences

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

Observatorio Astronomico Nacional

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

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 Institute

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

Instituto de Radioastronomia Milimetrica

P. Saraceno

Istituto di Fisica dello Spazio Interplanetario, Rome

R. Shipman

Netherlands Institute for Space Research (SRON)

F. F. S. van der Tak

University of Groningen

Netherlands Institute for Space Research (SRON)

F. Wyrowski

Max Planck Institute

U. A. Yildiz

Leiden University

M. Ciechanowicz

Max Planck Institute

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 Institute

P. Morris

CalTech

J. A. Murphy

Maynooth University

N. Trappe

Maynooth University

Astronomy and Astrophysics

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

Vol. 518 Article Number: L121 L121

Subject Categories

Astronomy, Astrophysics and Cosmology

DOI

10.1051/0004-6361/201014615