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Title: Si-BEARING MOLECULES TOWARD IRC+10216: ALMA UNVEILS THE MOLECULAR ENVELOPE OF CWLeo

We report the detection of SiS rotational lines in high-vibrational states as well as SiO and SiC{sub 2} lines in their ground vibrational state toward IRC+10216 during the Atacama Large Millimeter Array Cycle 0. The spatial distribution of these molecules shows compact emission for SiS and a more extended emission for SiO and SiC{sub 2} and also proves the existence of an increase in the SiC{sub 2} emission at the outer shells of the circumstellar envelope (CSE). We analyze the excitation conditions of the vibrationally excited SiS using the population diagram technique, and we use a large velocity gradient model to compare with the observations. We found moderate discrepancies between the observations and the models that could be explained if SiS lines detected are optically thick. Additionally, the line profiles of the detected rotational lines in the high-energy vibrational states show a decreasing linewidth with increasing energy levels. This may be evidence that these lines could be excited only in the inner shells, i.e., the densest and hottest, of the CSE of IRC+10216.
Authors:
; ; ;  [1] ; ;  [2] ;  [3] ;  [4] ; ; ;  [5] ;  [6]
  1. Group of Molecular Astrophysics, ICMM, CSIC, C/ Sor Juana Inés de la Cruz 3, E-28049 Cantoblanco, Madrid (Spain)
  2. Institut de Radioastronomie Millimétrique, 300 rue de la la Piscine, F-38406 Saint Martin d’Hères (France)
  3. Departamento de Estrellas y Medio Interestelar, Instituto de Astronomía, Universidad Nacional Autónoma de México (UNAM), Ciudad Universitaria, 04510, Mexico City, México (Mexico)
  4. Istituto di Radiastronomia, INAF–CNR, via Gobetti 101, I-40129 Bologna (Italy)
  5. Departamento de Química Física, Facultad de Química, Universidad de Murcia, Campus Espinardo, E-30100 Murcia (Spain)
  6. LOMC–UMR 6294, CNRS–Université du Havre, 25 rue Philippe Lebon, BP 1123, F-76063 Le Havre cedex (France)
Publication Date:
OSTI Identifier:
22518968
Resource Type:
Journal Article
Resource Relation:
Journal Name: Astrophysical Journal Letters; Journal Volume: 805; Journal Issue: 2; Other Information: Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
79 ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; COMPARATIVE EVALUATIONS; DIAGRAMS; EMISSION; EXCITATION; EXCITED STATES; MOLECULES; SILICON CARBIDES; SILICON OXIDES; SILICON SULFIDES; SPATIAL DISTRIBUTION; STARS; VIBRATIONAL STATES