Herschel/HIFI observations of high-J CO transitions in the protoplanetary nebula CRL 618
Artikel i vetenskaplig tidskrift, 2010
Aims. We aim to study the physical conditions, particularly the excitation state, of the intermediate-temperature gas components in the protoplanetary nebula CRL 618. These components are particularly important for understanding the evolution of the nebula. Methods. We performed Herschel/HIFI observations of several CO lines in the far-infrared/sub-mm in the protoplanetary nebula CRL 618. The high spectral resolution provided by HIFI allows measurement of the line profiles. Since the dynamics and structure of the nebula is well known from mm-wave interferometric maps, it is possible to identify the contributions of the different nebular components (fast bipolar outflows, double shells, compact slow shell) to the line profiles. The observation of these relatively high-energy transitions allows an accurate study of the excitation conditions in these components, particularly in the warm ones, which cannot be properly studied from the low-energy lines. Results. The (CO)-C-12 J = 16-15, 10-9, and 6-5 lines are easily detected in this source. Both (CO)-C-13 J = 10-9 and 6-5 are also detected. Wide profiles showing spectacular line wings have been found, particularly in (CO)-C-12 J = 16-15. Other lines observed simultaneously with CO are also shown. Our analysis of the CO high-J transitions, when compared with the existing models, confirms the very low expansion velocity of the central, dense component, which probably indicates that the shells ejected during the last AGB phases were driven by radiation pressure under a regime of maximum transfer of momentum. No contribution of the diffuse halo found from mm-wave data is identified in our spectra, because of its low temperature. We find that the fast bipolar outflow is quite hot, much hotter than previously estimated; for instance, gas flowing at 100 km s(-1) must have a temperature higher than similar to 200 K. Probably, this very fast outflow, with a kinematic age < 100 yr, has been accelerated by a shock and has not yet cooled down. The double empty shell found from mm-wave mapping must also be relatively hot, in agreement with the previous estimate.
stars: mass-loss
crl-618
circumstellar matter
planetary nebulae: general
facility
apex
heterodyne instrument
dynamics
planetary nebulae: individual: CRL 618
molecular envelope
stars: AGB and post-AGB
Författare
V. Bujarrabal
J. Alcolea
R. Soria-Ruiz
P. Planesas
Atacama Large Millimeter-submillimeter Array (ALMA)
D. Teyssier
Europeiska rymdorganisationen (ESA)
A. P. Marston
Europeiska rymdorganisationen (ESA)
J. Cernicharo
Centro de Astrobiologia (CAB)
L. Decin
KU Leuven
Universiteit Van Amsterdam
C. Dominik
Universiteit Van Amsterdam
Radboud Universiteit
Kay Justtanont
Chalmers, Rymd- och geovetenskap, Radioastronomi och astrofysik
A. de Koter
Universiteit Van Amsterdam
Sterrekundig Instituut Utrecht
G. J. Melnick
Harvard-Smithsonian Center for Astrophysics
K. M. Menten
Max-Planck-Gesellschaft
D. A. Neufeld
Johns Hopkins University
Hans Olofsson
Chalmers, Rymd- och geovetenskap, Onsala rymdobservatorium
M. Schmidt
Polish Academy of Sciences
Fredrik Schöier
Chalmers, Rymd- och geovetenskap, Onsala rymdobservatorium
R. Szczerba
Polish Academy of Sciences
Lbfm Waters
Universiteit Van Amsterdam
KU Leuven
G. Quintana-Lacaci
Institut de Radioastronomie Millimétrique (IRAM)
R. Güsten
Max-Planck-Gesellschaft
J. D. Gallego
Observatorio de Yebes (IGN)
M. C. Diez-Gonzalez
Observatorio de Yebes (IGN)
A. Barcia
Observatorio de Yebes (IGN)
I. Lopez-Fernandez
Observatorio de Yebes (IGN)
K. Wildeman
Netherlands Institute for Space Research (SRON)
Aggm Tielens
Universiteit Leiden
K. Jacobs
Universität zu Köln
Astronomy and Astrophysics
0004-6361 (ISSN) 1432-0746 (eISSN)
Vol. 521 1 Article Number: L3- L3Ämneskategorier (SSIF 2011)
Astronomi, astrofysik och kosmologi
DOI
10.1051/0004-6361/201015068