Silicon in the dust formation zone of IRC +10216
Leen Decin
(1)
,
José Cernicharo
(2)
,
Michael J. Barlow
(3)
,
Pierre Royer
(1)
,
Bart Vandenbussche
(1)
,
R. Wesson
(3)
,
Edward T. Polehampton
(4)
,
E. de Beck
(1)
,
Marcelino Agúndez
(2, 5)
,
J. A. D. L. Blommaert
(1)
,
Mathieu Cohen
(6)
,
Fabien Daniel
(2)
,
W. de Meester
(1)
,
K. M. Exter
(1)
,
Helmut Feuchtgruber
(7)
,
J. P. Fonfría
(8)
,
Walter K. Gear
(9)
,
Javier R. Goicoechea
(2)
,
H. L. Gomez
(9)
,
M. A. T. Groenewegen
(10)
,
Peter C. Hargrave
(9)
,
R. Huygen
(1)
,
P. Imhof
(11)
,
Robert J. Ivison
(12)
,
C. Jean
(1)
,
Franz Kerschbaum
(13)
,
Sarah J. Leeks
(4)
,
Tanya L. Lim
(4)
,
Mikako Matsuura
(3)
,
Goran Olofsson
(14)
,
Thomas Posch
(13)
,
S. Regibo
(1)
,
Giorgio Savini
(3)
,
B. Sibthorpe
(12)
,
Bruce Swinyard
(4)
,
Belén Tercero
(2)
,
Christoffel Waelkens
(1)
,
D. K. Witherick
(3)
,
J. A. Yates
(3)
1
Instituut voor Sterrenkunde, Katholieke Universiteit Leuven
2 LAM - Laboratorio de Astrofísica Molecular, CAB-CSIC/INTA
3 UCL - University College of London [London]
4 Space Science and Technology Department, Rutherford Appleton Laboratory
5 LUTH (UMR_8102) - Laboratoire Univers et Théories
6 Radio Astronomy Laboratory, University of California, Berkeley
7 MPE - Max-Planck-Institut für Extraterrestriche Physik
8 Departamento de Astrofisica Molecular e Infrarroja-Instituto de Estructura de la Materia, Consejo Superior de Investigaciones Científica (CSIC)
9 Cardiff University
10 ROB - Royal Observatory of Belgium = Observatoire Royal de Belgique
11 BSS - Blue Sky Spectroscopy
12 UKATC - UK Astronomy Technology Centre, Royal Observatory Edinburgh
13 IfA - Institut für Astronomie, Universität Wien
14 Stockholm University
2 LAM - Laboratorio de Astrofísica Molecular, CAB-CSIC/INTA
3 UCL - University College of London [London]
4 Space Science and Technology Department, Rutherford Appleton Laboratory
5 LUTH (UMR_8102) - Laboratoire Univers et Théories
6 Radio Astronomy Laboratory, University of California, Berkeley
7 MPE - Max-Planck-Institut für Extraterrestriche Physik
8 Departamento de Astrofisica Molecular e Infrarroja-Instituto de Estructura de la Materia, Consejo Superior de Investigaciones Científica (CSIC)
9 Cardiff University
10 ROB - Royal Observatory of Belgium = Observatoire Royal de Belgique
11 BSS - Blue Sky Spectroscopy
12 UKATC - UK Astronomy Technology Centre, Royal Observatory Edinburgh
13 IfA - Institut für Astronomie, Universität Wien
14 Stockholm University
Résumé
The interstellar medium is enriched primarily by matter ejected from evolved low and intermediate mass stars. The outflows from these stars create a circumstellar envelope in which a rich gas-phase and dust-nucleation chemistry takes place. We observed the nearest carbon-rich evolved star, IRC +10216, using the PACS (55-210 mum) and SPIRE (194-672 mum) spectrometers on board Herschel. We find several tens of lines from SiS and SiO, including lines from the v = 1 vibrational level. For SiS these transitions range up to J = 124-123, corresponding to energies around 6700 K, while the highest detectable transition is J = 90-89 for SiO, which corresponds to an energy around 8400 K. Both species trace the dust formation zone of IRC +10216, and the broad energy ranges involved in their detected transitions permit us to derive the physical properties of the gas and the particular zone in which each species has been formed. This allows us to check the accuracy of chemical thermodynamical equilibrium models and the suggested depletion of SiS and SiO due to accretion onto dust grains.