Reversal of infall in SgrB2(M) revealed by Herschel/HIFI observations of HCN lines at THz frequencies
Journal article, 2010
Aims. To investigate the accretion and feedback processes in massive star formation, we analyze the shapes of emission lines from hot molecular cores, whose asymmetries trace infall and expansion motions. Methods. The high-mass star forming region SgrB2(M) was observed with Herschel/HIFI (HEXOS key project) in various lines of HCN and its isotopologues, complemented by APEX data. The observations are compared to spherically symmetric, centrally heated models with density power-law gradient and different velocity fields (infall or infall+expansion), using the radiative transfer code RATRAN. Results. The HCN line profiles are asymmetric, with the emission peak shifting from blue to red with increasing J and decreasing line opacity (HCN to (HCN)-C-13). This is most evident in the HCN 12-11 line at 1062 GHz. These line shapes are reproduced by a model whose velocity field changes from infall in the outer part to expansion in the inner part. Conclusions. The qualitative reproduction of the HCN lines suggests that infall dominates in the colder, outer regions, but expansion dominates in the warmer, inner regions. We are thus witnessing the onset of feedback in massive star formation, starting to reverse the infall and finally disrupting the whole molecular cloud. To obtain our result, the THz lines uniquely covered by HIFI were critically important.
submillimeter: ISM
molecular-spectroscopy
outflow
ISM: kinematics and dynamics
ISM:
star-formation
cologne database
cdms
stars: formation
facility
b2
ISM: structure
molecules
ISM: individual objects: SgrB2(M)
Author
R. Rolffs
Max Planck Society
University of Cologne
P. Schilke
Max Planck Society
University of Cologne
C. Comito
Max Planck Society
E. A. Bergin
University of Michigan
F. F. S. van der Tak
Netherlands Institute for Space Research (SRON)
D. C. Lis
California Institute of Technology (Caltech)
S. L. Qin
University of Cologne
K. M. Menten
Max Planck Society
R. Güsten
Max Planck Society
T. A. Bell
California Institute of Technology (Caltech)
G. A. Blake
California Institute of Technology (Caltech)
E. Caux
Institut National des Sciences de l'Univers
University of Toulouse
C. Ceccarelli
Laboratoire d'Astrophysique de l'Observatoire de Grenoble
J. Cernicharo
Centro de Astrobiologia (CAB)
N. R. Crockett
University of Michigan
F. Daniel
Centro de Astrobiologia (CAB)
LERMA - Laboratoire d'Etudes du Rayonnement et de la Matiere en Astrophysique et Atmospheres
M. L. Dubernet
Observatoire de Paris-Meudon
Pierre and Marie Curie University (UPMC)
M. Emprechtinger
California Institute of Technology (Caltech)
P. Encrenaz
LERMA - Laboratoire d'Etudes du Rayonnement et de la Matiere en Astrophysique et Atmospheres
M. Gerin
LERMA - Laboratoire d'Etudes du Rayonnement et de la Matiere en Astrophysique et Atmospheres
T. F. Giesen
University of Cologne
J. R. Goicoechea
Centro de Astrobiologia (CAB)
P. F. Goldsmith
California Institute of Technology (Caltech)
H. Gupta
California Institute of Technology (Caltech)
E. Herbst
Ohio State University
C. Joblin
Institut National des Sciences de l'Univers
University of Toulouse
D. Johnstone
National Research Council Canada
W. D. Langer
California Institute of Technology (Caltech)
W. D. Latter
California Institute of Technology (Caltech)
S. D. Lord
California Institute of Technology (Caltech)
S. Maret
Laboratoire d'Astrophysique de l'Observatoire de Grenoble
P. G. Martin
Canadian Institute for Theoretical Astrophysics
G. J. Melnick
Harvard-Smithsonian Center for Astrophysics
P. Morris
California Institute of Technology (Caltech)
Holger Muller
University of Cologne
J. A. Murphy
Maynooth University
V. Ossenkopf
Netherlands Institute for Space Research (SRON)
University of Cologne
J. C. Pearson
California Institute of Technology (Caltech)
M. Perault
LERMA - Laboratoire d'Etudes du Rayonnement et de la Matiere en Astrophysique et Atmospheres
T. G. Phillips
California Institute of Technology (Caltech)
R. Plume
University of Calgary
S. Schlemmer
University of Cologne
J. Stutzki
University of Cologne
N. Trappe
Maynooth University
C. Vastel
University of Toulouse
Institut National des Sciences de l'Univers
S. Wang
University of Michigan
H. W. Yorke
California Institute of Technology (Caltech)
S. Yu
California Institute of Technology (Caltech)
J. Zmuidzinas
California Institute of Technology (Caltech)
M. C. Diez-Gonzalez
Yebes Observatory
R. Bachiller
Yebes Observatory
J. Martin-Pintado
Spanish National Research Council (CSIC)
W. Baechtold
Swiss Federal Institute of Technology in Zürich (ETH)
Michael Olberg
Chalmers, Earth and Space Sciences, Onsala Space Observatory
L. H. Nordh
Stockholm University
John Gill
California Institute of Technology (Caltech)
Goutam Chattopadhyay
California Institute of Technology (Caltech)
Astronomy and Astrophysics
0004-6361 (ISSN) 1432-0746 (eISSN)
Vol. 521 1 Article Number: L46 - L46Subject Categories (SSIF 2011)
Astronomy, Astrophysics and Cosmology
DOI
10.1051/0004-6361/201015106