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Reversal of infall in SgrB2(M) revealed by Herschel/HIFI observations of HCN lines at THz frequencies

Rolffs, R. and Lis, D. C. and Bell, T. A. and Blake, G. A. and Emprechtinger, M. and Latter, W. D. and Lord, S. D. and Morris, P. and Phillips, T. G. and Zmuidzinas, J. (2010) Reversal of infall in SgrB2(M) revealed by Herschel/HIFI observations of HCN lines at THz frequencies. Astronomy and Astrophysics, 521 . L46. ISSN 0004-6361. doi:10.1051/0004-6361/201015106.

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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 H^(13)CN). 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.

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Lis, D. C.0000-0002-0500-4700
Blake, G. A.0000-0003-0787-1610
Additional Information:© 2010 ESO. Received 31 May 2010; Accepted 7 July 2010; Published online 01 October 2010. Herschel is an ESA space observatory with science instruments provided by European-led Principal Investigator consortia and with important participation from NASA. HIFI has been designed and built by a consortium of institutes and university departments from across Europe, Canada and the United States under the leadership of SRON Netherlands Institute for Space Research, Groningen, The Netherlands and with major contributions from Germany, France and the US. Consortium members are: Canada: CSA, U. Waterloo; France: CESR, LAB, LERMA, IRAM; Germany: KOSMA, MPIfR, MPS; Ireland, NUI Maynooth; Italy: ASI, IFSI-INAF, Osservatorio Astrofisico di Arcetri- INAF; Netherlands: SRON, TUD; Poland: CAMK, CBK; Spain: Observatorio Astronòmico Nacional (IGN), Centro de Astrobiologìa (CSIC-INTA). Sweden: Chalmers University of Technology - MC2, RSS & GARD; Onsala Space Observatory; Swedish National Space Board, Stockholm University - Stockholm Observatory; Switzerland: ETH Zurich, FHNW; USA: Caltech, JPL, NHSC. Support for this work was provided by NASA through an award issued by JPL/Caltech. CSO is supported by the NSF, award AST-0540882.
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Subject Keywords:stars: formation; ISM: kinematics and dynamics; ISM: structure; ISM: molecules; ISM: individual objects: SgrB2(M); submillimeter: ISM
Record Number:CaltechAUTHORS:20101223-095516215
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Official Citation:Reversal of infall in SgrB2(M) revealed by Herschel/HIFI observations of HCN lines at THz frequencies R. Rolffs, P. Schilke, C. Comito, E. A. Bergin, F. F. S. van der Tak, D. C. Lis, S.-L. Qin, K. M. Menten, R. Güsten, T. A. Bell, G. A. Blake, E. Caux, C. Ceccarelli, J. Cernicharo, N. R. Crockett, F. Daniel, M.-L. Dubernet, M. Emprechtinger, P. Encrenaz, M. Gerin, T. F. Giesen, J. R. Goicoechea, P. F. Goldsmith, H. Gupta, E. Herbst, C. Joblin, D. Johnstone, W. D. Langer, W. D. Latter, S. D. Lord, S. Maret, P. G. Martin, G. J. Melnick, P. Morris, H. S. P. Müller, J. A. Murphy, V. Ossenkopf, J. C. Pearson, M. Pérault, T. G. Phillips, R. Plume, S. Schlemmer, J. Stutzki, N. Trappe, C. Vastel, S. Wang, H. W. Yorke, S. Yu, J. Zmuidzinas, M. C. Diez-Gonzalez, R. Bachiller, J. Martin-Pintado, W. Baechtold, M. Olberg, L. H. Nordh, J. J. Gill and G. Chattopadhyay A&A 521 L46 (2010) DOI: 10.1051/0004-6361/201015106
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:21516
Deposited On:03 Jan 2011 15:55
Last Modified:09 Nov 2021 15:57

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