title: SI-BEARING MOLECULES TOWARD IRC+10216: ALMA UNVEILS THE MOLECULAR ENVELOPE OF CWLEO.
abstract: We report the detection of SiS rotational lines in high-vibrational states as well as SiO and SiC2lines 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 SiC2, and also proves the existence of an increase in the SiC2emission at the outer shells of the circumstellar envelope. 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 circumstellar envelope of IRC+10216.
authors.affiliation: Group of Molecular Astrophysics. ICMM, CSIC. C/ Sor Juana Inés de la Cruz 3, 28049 Cantoblanco, Madrid, Spain ; Centro de Astrobiología, INTA-CSIC. E-28691 Villanueva de la Cañada, Madrid, Spain.
authors.forename: L Velilla
authors.initials: LV
authors.lastname: Prieto
authors.affiliation: Group of Molecular Astrophysics. ICMM, CSIC. C/ Sor Juana Inés de la Cruz 3, 28049 Cantoblanco, Madrid, Spain.
authors.forename: J
authors.initials: J
authors.lastname: Cernicharo
authors.affiliation: Group of Molecular Astrophysics. ICMM, CSIC. C/ Sor Juana Inés de la Cruz 3, 28049 Cantoblanco, Madrid, Spain.
authors.forename: G
authors.initials: G
authors.lastname: Quintana-Lacaci
authors.affiliation: Group of Molecular Astrophysics. ICMM, CSIC. C/ Sor Juana Inés de la Cruz 3, 28049 Cantoblanco, Madrid, Spain.
authors.forename: M
authors.initials: M
authors.lastname: Agúndez
authors.affiliation: Institut de Radioastronomie Millimétrique. 300 rue de la la Piscine, F-38406, Saint Martin d'Hères, France.
authors.forename: A
authors.initials: A
authors.lastname: Castro-Carrizo
authors.affiliation: Departamento de Estrellas y Medio Interestelar, Instituto de Astronomía, Universidad Nacional Autónoma de México (UNAM). Ciudad Universitaria, 04510, Mexico City, México.
authors.forename: J P
authors.initials: JP
authors.lastname: Fonfŕia
authors.affiliation: Istituto di Radiastronomia, INAF-CNR, via Gobetti 101, 40129 Bologna, Italy.
authors.forename: N
authors.initials: N
authors.lastname: Marcelino
authors.affiliation: Departamento de Química Física, Facultad de Química, Universidad de Murcia. Campus Espinardo, 30100 Murcia, Spain.
authors.forename: J
authors.initials: J
authors.lastname: Zúñiga
authors.affiliation: Departamento de Química Física, Facultad de Química, Universidad de Murcia. Campus Espinardo, 30100 Murcia, Spain.
authors.forename: A
authors.initials: A
authors.lastname: Requena
authors.affiliation: Departamento de Química Física, Facultad de Química, Universidad de Murcia. Campus Espinardo, 30100 Murcia, Spain.
authors.forename: A
authors.initials: A
authors.lastname: Bastida
authors.affiliation: LOMC-UMR 6294, CNRS-Université du Havre, 25 rue Philippe Lebon, BP. 1123, 76063 Le Havre cedex, France.
authors.forename: F
authors.initials: F
authors.lastname: Lique
authors.affiliation: Institut de Radioastronomie Millimétrique. 300 rue de la la Piscine, F-38406, Saint Martin d'Hères, France ; LERMA, Observatoire de Paris, PSL Research University, CNRS, UMR 8112, F-75014, Paris, France.
authors.forename: M
authors.initials: M
authors.lastname: Guélin
keywords: astrochemistry; circumstellar matter; line: identification; molecular processes; stars: AGB and post-AGB; stars: individual (IRC+10216)