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Flowers AM, Brown A, Klobukowski M. Anharmonic Vibrational Spectroscopy of Germanium-Containing Clusters, Ge xC 4-x and Ge xSi 4-x ( x = 0-4), for Interstellar Detection. J Phys Chem A 2024; 128:5351-5361. [PMID: 38942734 DOI: 10.1021/acs.jpca.4c02081] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/30/2024]
Abstract
An extensive, high-level theoretical study on tetra-atomic germanium carbide/silicide clusters is presented. Accurate harmonic and anharmonic vibrational frequencies and rotational constants are calculated at the CCSD(T)-F12a(b)/cc-pVT(Q)Z-F12 levels of theory. With growing capabilities to discern more of the chemical composition of the interstellar medium (ISM), an accurate database of reference material is required. The presence of carbon is ubiquitous in the ISM, and silicon is known to be present in interstellar dust grains; however, germanium-containing molecules remain elusive. To begin understanding the presence and role of germanium in the ISM, we present this study of the vibrational and rotational spectroscopic properties of various germanium-containing molecules to aid in their potential identification in the ISM with modern observational tools such as the James Webb Space Telescope. Structures studied herein include rhomboidal (r-), diamond (d-), and trapezoidal (t-) tetra-atomic molecules of the form GexC4-x and GexSi4-x, where x = 0-4. The most promising structure for detection is r-Ge2C2 via the ν4 mode with a frequency of 802.7 cm-1 (12.5 μm) and an intensity of 307.2 km mol-1. Other molecules that are potentially detectable, i.e., through vibrational modes or rotational transitions, include r-Ge3C, r-GeSi3, d-GeC3, r-GeC3, and t-Ge2C2.
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Affiliation(s)
- A Mackenzie Flowers
- Department of Chemistry, University of Alberta, Edmonton, Alberta T6G 2G2, Canada
| | - Alex Brown
- Department of Chemistry, University of Alberta, Edmonton, Alberta T6G 2G2, Canada
| | - Mariusz Klobukowski
- Department of Chemistry, University of Alberta, Edmonton, Alberta T6G 2G2, Canada
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2
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Mota VC, Caridade PJSB, Varandas AJC, Galvão BRL. Quasiclassical Trajectory Study of the Si + SH Reaction on an Accurate Double Many-Body Expansion Potential Energy Surface. J Phys Chem A 2022; 126:3555-3568. [PMID: 35612827 DOI: 10.1021/acs.jpca.2c01633] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
An accurate potential energy surface (PES) for the HSiS system based on MRCI+Q calculations extrapolated to the complete basis set limit is presented. Modeled with the double many-body expansion (DMBE) method, the PES provides an accurate description of the long-range interactions, including electrostatic and dispersion terms decaying as R-4, R-5, R-6, R-8, R-10 that are predicted from dipole moments, quadrupole moments, and dipolar polarizabilities, which are also calculated at the MRCI+Q level. The novel PES is then used in quasiclassical trajectory calculations to predict the rate coefficients of the Si + SH → SiS + H reaction, which has been shown to be a major source of the SiS in certain regions of the interstellar medium. An account of the zero-point energy leakage based on various nonactive models is also given. It is shown that the reaction is dominated by long-range forces, with the mechanism Si + SH → SiSH → SSiH → SiS + H being the most important one for all temperatures studied. Although SSiH corresponds to the global minimum of the PES, the contribution from the direct reaction Si + SH → SSiH → SiS + H is less than 0.5% for temperatures higher than 500 K. The rovibrational distributions of the products are calculated using the momentum Gaussian binning method and show that as the temperature is increased the average vibrational quantum number decreases while the rotational distribution spreads up to larger values.
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Affiliation(s)
- V C Mota
- Departamento de Física, Universidade Federal do Espírito Santo, 29075-910Vitória, Brazil
| | - P J S B Caridade
- Coimbra Chemistry Centre and Chemistry Department, University of Coimbra, 3004-535Coimbra, Portugal
| | - A J C Varandas
- Departamento de Física, Universidade Federal do Espírito Santo, 29075-910Vitória, Brazil.,Coimbra Chemistry Centre and Chemistry Department, University of Coimbra, 3004-535Coimbra, Portugal.,School of Physics and Physical Engineering, Qufu Normal University, Qufu273165, P. R. China
| | - B R L Galvão
- Centro Federal de Educação Tecnológica de Minas Gerais, CEFET-MG, Av. Amazonas 5253, 30421-169Belo Horizonte-MG, Brazil
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3
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Petkowski JJ, Bains W, Seager S. On the Potential of Silicon as a Building Block for Life. Life (Basel) 2020; 10:E84. [PMID: 32532048 PMCID: PMC7345352 DOI: 10.3390/life10060084] [Citation(s) in RCA: 23] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/16/2020] [Revised: 06/05/2020] [Accepted: 06/08/2020] [Indexed: 12/21/2022] Open
Abstract
Despite more than one hundred years of work on organosilicon chemistry, the basis for the plausibility of silicon-based life has never been systematically addressed nor objectively reviewed. We provide a comprehensive assessment of the possibility of silicon-based biochemistry, based on a review of what is known and what has been modeled, even including speculative work. We assess whether or not silicon chemistry meets the requirements for chemical diversity and reactivity as compared to carbon. To expand the possibility of plausible silicon biochemistry, we explore silicon's chemical complexity in diverse solvents found in planetary environments, including water, cryosolvents, and sulfuric acid. In no environment is a life based primarily around silicon chemistry a plausible option. We find that in a water-rich environment silicon's chemical capacity is highly limited due to ubiquitous silica formation; silicon can likely only be used as a rare and specialized heteroatom. Cryosolvents (e.g., liquid N2) provide extremely low solubility of all molecules, including organosilicons. Sulfuric acid, surprisingly, appears to be able to support a much larger diversity of organosilicon chemistry than water.
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Affiliation(s)
- Janusz Jurand Petkowski
- Department of Earth, Atmospheric, and Planetary Sciences, Massachusetts Institute of Technology, 77 Mass. Ave., Cambridge, MA 02139, USA; (W.B.); (S.S.)
| | - William Bains
- Department of Earth, Atmospheric, and Planetary Sciences, Massachusetts Institute of Technology, 77 Mass. Ave., Cambridge, MA 02139, USA; (W.B.); (S.S.)
| | - Sara Seager
- Department of Earth, Atmospheric, and Planetary Sciences, Massachusetts Institute of Technology, 77 Mass. Ave., Cambridge, MA 02139, USA; (W.B.); (S.S.)
- Department of Physics, Massachusetts Institute of Technology, 77 Mass. Ave., Cambridge, MA 02139, USA
- Department of Aeronautics and Astronautics, Massachusetts Institute of Technology, 77 Mass. Ave., Cambridge, MA 02139, USA
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Agúndez M, Martínez JI, de Andres PL, Cernicharo J, Martín-Gago JA. Chemical equilibrium in AGB atmospheres: Successes, failures, and prospects for small molecules, clusters, and condensates. ASTRONOMY AND ASTROPHYSICS 2020; 637:A59. [PMID: 32508346 PMCID: PMC7274841] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Subscribe] [Scholar Register] [Indexed: 06/11/2023]
Abstract
Chemical equilibrium has proven extremely useful for predicting the chemical composition of AGB atmospheres. Here we use a recently developed code and an updated thermochemical database that includes gaseous and condensed species involving 34 elements to compute the chemical equilibrium composition of AGB atmospheres of M-, S-, and C-type stars. We include for the first time Ti x C y clusters, with x = 1-4 and y = 1-4, and selected larger clusters ranging up to Ti13C22, for which thermochemical data are obtained from quantum-chemical calculations. Our main aims are to systematically survey the main reservoirs of each element in AGB atmospheres, review the successes and failures of chemical equilibrium by comparing it with the latest observational data, identify potentially detectable molecules that have not yet been observed, and diagnose the most likely gas-phase precursors of dust and determine which clusters might act as building blocks of dust grains. We find that in general, chemical equilibrium reproduces the observed abundances of parent molecules in circumstellar envelopes of AGB stars well. There are, however, severe discrepancies of several orders of magnitude for some parent molecules that are observed to be anomalously overabundant with respect to the predictions of chemical equilibrium. These are HCN, CS, NH3, and SO2 in M-type stars, H2O and NH3 in S-type stars, and the hydrides H2O, NH3, SiH4, and PH3 in C-type stars. Several molecules have not yet been observed in AGB atmospheres but are predicted with non-negligible abundances and are good candidates for detection with observatories such as ALMA. The most interesting ones are SiC5, SiNH, SiCl, PS, HBO, and the metal-containing molecules MgS, CaS, CaOH, CaCl, CaF, ScO, ZrO, VO, FeS, CoH, and NiS. In agreement with previous studies, the first condensates predicted to appear in C-rich atmospheres are found to be carbon, TiC, and SiC, while Al2O3 is the first major condensate expected in O-rich outflows. According to our chemical equilibrium calculations, the gas-phase precursors of carbon dust are probably acetylene, atomic carbon, and/or C3, while for silicon carbide dust, the most likely precursors are the molecules SiC2 and Si2C. In the case of titanium carbide dust, atomic Ti is the major reservoir of this element in the inner regions of AGB atmospheres, and therefore it is probably the main supplier of titanium during the formation of TiC dust. However, chemical equilibrium predicts that large titanium-carbon clusters such as Ti8C12 and Ti13C22 become the major reservoirs of titanium at the expense of atomic Ti in the region where condensation of TiC is expected to occur. This suggests that the assembly of large Ti x C y clusters might be related to the formation of the first condensation nuclei of TiC. In the case of Al2O3 dust, chemical equilibrium indicates that atomic Al and the carriers of Al-O bonds AlOH, AlO, and Al2O are the most likely gas-phase precursors.
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Affiliation(s)
- M Agúndez
- Instituto de Física Fundamental, CSIC, C/ Serrano 123, 28006 Madrid, Spain
| | - J I Martínez
- Instituto de Ciencia de Materiales de Madrid, CSIC, C/ Sor Juana Inés de la Cruz 3, 28049 Cantoblanco, Spain
| | - P L de Andres
- Instituto de Ciencia de Materiales de Madrid, CSIC, C/ Sor Juana Inés de la Cruz 3, 28049 Cantoblanco, Spain
| | - J Cernicharo
- Instituto de Física Fundamental, CSIC, C/ Serrano 123, 28006 Madrid, Spain
| | - J A Martín-Gago
- Instituto de Ciencia de Materiales de Madrid, CSIC, C/ Sor Juana Inés de la Cruz 3, 28049 Cantoblanco, Spain
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Job N, Karton A, Thirumoorthy K, Cooksy AL, Thimmakondu VS. Theoretical Studies of SiC 4H 2 Isomers Delineate Three Low-Lying Silylidenes Are Missing in the Laboratory. J Phys Chem A 2020; 124:987-1002. [PMID: 31904236 DOI: 10.1021/acs.jpca.9b11742] [Citation(s) in RCA: 17] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Eleven isomers of SiC4H2 lying within 50 kcal mol-1 have been theoretically investigated using density functional theory and high-level coupled-cluster methods. Among them, four isomers, 1-ethynyl-3-silacycloprop-1(2)-en-3-ylidene (1), diethynylsilylidene (2), 1-sila-1,2,3,4-pentatetraenylidene (4), and 1,3-butadiynylsilylidene (5), have already been identified in the laboratory. The current investigation reports three low-lying (<1 eV) silylidenes [2-methylenesilabicyclo[1.1.0]but-1(3)-en-4-ylidene (3), 4-sila-2-methylenebicyclo[1.1.0]but-1(3)-en-4-ylidene (6), and 3-ethynyl-1-silapropadienylidene (7)] and three high-lying (>1 eV) silylidenes [2-sila-(didehydrovinylidene)cyclopropene (8), an isomer with a planar tetracoordinate carbon (ptC) atom (10), and 1-ethynyl-1-silapropadienylidene (11)], which remain elusive in the laboratory to date. Isomer 9 also contains a ptC atom, which turned out to be a transition state at all levels. Though all isomers are polar (μ ≠ 0), rotational spectrum is available only for 4. Using matrix isolation, three isomers (1, 2, and 5) have been trapped in the laboratory at 10 K. Considering the astrochemical relevance of silicon-carbide clusters in the interstellar medium, the current theoretical data demand new molecular spectroscopic studies on SiC4H2. Surprisingly, unlike the isovalent C5H2 isomers, where the bent carbenes are yet to be identified in the laboratory, the bent silylidenes (2 and 5) have been trapped in the case of SiC4H2. In both the cases, molecules with transannular C-C and/or Si-C bonds remain elusive, though they lie in the low-lying region. Using suitable precursors, whether these peculiar geometries (especially 3 and 6) would be identified or not in the laboratory needs to be addressed by molecular spectroscopists. The present investigation documents structural and spectroscopic information of SiC4H2 isomers, which may compliment future molecular spectroscopic observations including radioastronomical searches.
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Affiliation(s)
- Nisha Job
- Department of Chemistry, School of Advanced Sciences , Vellore Institute of Technology , Vellore 632014 , Tamil Nadu , India
| | - Amir Karton
- School of Molecular Sciences , The University of Western Australia , Perth , Western Australia 6009 , Australia
| | - Krishnan Thirumoorthy
- Department of Chemistry, School of Advanced Sciences , Vellore Institute of Technology , Vellore 632014 , Tamil Nadu , India
| | - Andrew L Cooksy
- Department of Chemistry and Biochemistry , San Diego State University , San Diego , California 92182-1030 , United States
| | - Venkatesan S Thimmakondu
- Department of Chemistry and Biochemistry , San Diego State University , San Diego , California 92182-1030 , United States
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Cernicharo J, Cabezas C, Pardo JR, Agúndez M, Bermúdez C, Velilla-Prieto L, Tercero F, López-Pérez JA, Gallego JD, Fonfría JP, Quintana-Lacaci G, Guélin M, Endo Y. Discovery of two new magnesium-bearing species in IRC+10216: MgC 3N and MgC 4H. ASTRONOMY AND ASTROPHYSICS 2019; 630:L2. [PMID: 31579315 PMCID: PMC6774763 DOI: 10.1051/0004-6361/201936372] [Citation(s) in RCA: 20] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/25/2023]
Abstract
We report on the detection of two series of harmonically related doublets in IRC +10216. From the observed frequencies, the rotational constant of the first series is B = 1380.888 MHz and that of the second series is B = 1381.512 MHz. The two series correspond to two species with a 2Σ electronic ground state. After considering all possible candidates, and based on quantum chemical calculations, the first series is assigned to MgC3N and the second to MgC4H. For the latter species, optical spectroscopy measurements support its identification. Unlike diatomic metal-containing molecules, the line profiles of the two new molecules indicate that they are formed in the outer layers of the envelope, as occurs for MgNC and other polyatomic metal-cyanides. We also confirm the detection of MgCCH that was previously reported from the observation of two doublets. The relative abundance of MgC3N with respect to MgNC is close to one while that of MgC4H relative to MgCCH is about ten. The synthesis of these magnesium cyanides and acetylides in IRC +10216 can be explained in terms of a two-step process initiated by the radiative association of Mg+ with large cyanopolyynes and polyynes followed by the dissociative recombination of the ionic complexes.
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Affiliation(s)
- J. Cernicharo
- Grupo de Astrofísica Molecular. Instituto de Física Fundamental (IFF-CSIC). C/Serrano 121, 28006 Madrid, Spain
| | - C. Cabezas
- Grupo de Astrofísica Molecular. Instituto de Física Fundamental (IFF-CSIC). C/Serrano 121, 28006 Madrid, Spain
| | - J. R. Pardo
- Grupo de Astrofísica Molecular. Instituto de Física Fundamental (IFF-CSIC). C/Serrano 121, 28006 Madrid, Spain
| | - M. Agúndez
- Grupo de Astrofísica Molecular. Instituto de Física Fundamental (IFF-CSIC). C/Serrano 121, 28006 Madrid, Spain
| | - C. Bermúdez
- Grupo de Astrofísica Molecular. Instituto de Física Fundamental (IFF-CSIC). C/Serrano 121, 28006 Madrid, Spain
| | - L. Velilla-Prieto
- Grupo de Astrofísica Molecular. Instituto de Física Fundamental (IFF-CSIC). C/Serrano 121, 28006 Madrid, Spain
- Department of Space, Earth and Environment, Chalmers University of Technology, Onsala Space Observatory, 439 92 Onsala, Sweden
| | - F. Tercero
- Centro de Desarrollos Tecnológicos, Observatorio de Yebes (IGN), 19141 Yebes, Guadalajara, Spain
| | - J. A. López-Pérez
- Centro de Desarrollos Tecnológicos, Observatorio de Yebes (IGN), 19141 Yebes, Guadalajara, Spain
| | - J. D. Gallego
- Centro de Desarrollos Tecnológicos, Observatorio de Yebes (IGN), 19141 Yebes, Guadalajara, Spain
| | - J. P. Fonfría
- Grupo de Astrofísica Molecular. Instituto de Física Fundamental (IFF-CSIC). C/Serrano 121, 28006 Madrid, Spain
| | - G. Quintana-Lacaci
- Grupo de Astrofísica Molecular. Instituto de Física Fundamental (IFF-CSIC). C/Serrano 121, 28006 Madrid, Spain
| | - M. Guélin
- Institut de Radioastronomie Millimétrique, 300 rue de la Piscine, F-38406, Saint Martin d’Hères, France
| | - Y. Endo
- Department of Applied Chemistry, Science Building II, National Chiao Tung University, 1001 Ta-Hsueh Rd., Hsinchu 30010, Taiwan
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Cernicharo J, Velilla-Prieto L, Agúndez M, Pardo J, Fonfría J, Quintana-Lacaci G, Cabezas C, Bermúdez C, Guélin M. Discovery of the first Ca-bearing molecule in space: CaNC. ASTRONOMY AND ASTROPHYSICS 2019; 627:L4. [PMID: 31327871 PMCID: PMC6640036 DOI: 10.1051/0004-6361/201936040] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
Abstract
We report on the detection of calcium isocyanide, CaNC, in the carbon-rich evolved star IRC+10216. We derived a column density for this species of (2±0.5)×1011 cm-2. Based on the observed line profiles and the modelling of its emission through the envelope, the molecule has to be produced in the intermediate and outer layers of the circumstellar envelope where other metal-isocyanides have previously been found in this source. The abundance ratio of CaNC relative to MgNC and FeCN is ≃1/60 and ≃1, respectively. We searched for the species CaF, CaCl, CaC, CaCCH, and CaCH3 for which accurate frequency predictions are available. Only upper limits have been obtained for these molecules.
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Affiliation(s)
- J. Cernicharo
- Grupo de Astrofísica Molecular. Instituto de Física Fundamental (IFF-CSIC). C/Serrano 121, 28006 Madrid, Spain
| | - L. Velilla-Prieto
- Grupo de Astrofísica Molecular. Instituto de Física Fundamental (IFF-CSIC). C/Serrano 121, 28006 Madrid, Spain
- Department of Space, Earth and Environment, Chalmers University of Technology, Onsala Space Observatory, 439 92 Onsala, Sweden
| | - M. Agúndez
- Grupo de Astrofísica Molecular. Instituto de Física Fundamental (IFF-CSIC). C/Serrano 121, 28006 Madrid, Spain
| | - J.R. Pardo
- Grupo de Astrofísica Molecular. Instituto de Física Fundamental (IFF-CSIC). C/Serrano 121, 28006 Madrid, Spain
| | - J.P. Fonfría
- Grupo de Astrofísica Molecular. Instituto de Física Fundamental (IFF-CSIC). C/Serrano 121, 28006 Madrid, Spain
| | - G. Quintana-Lacaci
- Grupo de Astrofísica Molecular. Instituto de Física Fundamental (IFF-CSIC). C/Serrano 121, 28006 Madrid, Spain
| | - C. Cabezas
- Grupo de Astrofísica Molecular. Instituto de Física Fundamental (IFF-CSIC). C/Serrano 121, 28006 Madrid, Spain
| | - C. Bermúdez
- Grupo de Astrofísica Molecular. Instituto de Física Fundamental (IFF-CSIC). C/Serrano 121, 28006 Madrid, Spain
| | - M. Guélin
- Institut de Radioastronomie Millimétrique, 300 rue de la Piscine, F-38406, Saint Martin d’Hères, France
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Anusuri B. Quantum dynamical study of rotational excitations in SiS ( X 1Σ +) molecule by H collisions. Heliyon 2019; 5:e01647. [PMID: 31193019 PMCID: PMC6513813 DOI: 10.1016/j.heliyon.2019.e01647] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/13/2019] [Revised: 04/05/2019] [Accepted: 05/01/2019] [Indexed: 11/25/2022] Open
Abstract
The knowledge of accurate rate coefficients for collisional excitation of molecules by the abundant chemical species like He, H2 and H is important in modeling the conditions of interstellar medium. In the present paper, we computed the inelastic rotational cross sections and the corresponding rate coefficients of SiS molecule in its ground vibrational state in collisions with atomic hydrogen, H. We computed ab initio two-dimensional (rigid-rotor) potential energy surface for the H + SiS system at high accuracy for this purpose. The excitation cross sections are performed by numerically exact close-coupling quantum mechanical formalism up to collision energy of 2000 cm-1. The corresponding rate coefficients are obtained in the temperature range 5-300 K.
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Affiliation(s)
- Bhargava Anusuri
- Department of Chemistry, Indian Institute of Technology Madras, Chennai, 600036, India
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9
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McCarthy MC, Gottlieb CA, Cernicharo J. Building Blocks of Dust: A Coordinated Laboratory and Astronomical Study of AGB Stars. JOURNAL OF MOLECULAR SPECTROSCOPY 2019; 356:7-20. [PMID: 30956352 PMCID: PMC6450511] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Subscribe] [Scholar Register] [Indexed: 06/09/2023]
Abstract
This article provides an overview of recent astronomical studies and a closely coordinated laboratory program devoted to the study of the physics and chemistry of carbon rich Asymptotic Giant Branch (AGB) stars. The increased sensitivity and angular resolution of high altitude ground-based millimeter-wave interferometers in the past few years has enabled molecular astronomers to determine the excitation and spatial distribution of molecules within a few stellar radii of the central star where the molecular seeds of dust are formed, and to critically assess the physicochemical mechanisms of dust formation and growth. However the astronomical studies are crucially dependent on precise laboratory measurements of the rotational spectra - both in the ground and vibrationally excited states of the normal and rare isotopic species - of the principal molecules in the inner region which appear to contain only two or three heavy atoms Much remains to be done by laboratory spectroscopists as evidenced by the large number of unassigned millimeters-wave rotational lines that are observed in the inner envelope of carbon rich AGB stars. As an illustration we refer to the example of an initial laboratory approach for establishing whether vibrationally excited SiC2 and HCN are the carriers of some of the unassigned features observed in the prototypical carbon rich AGB star IRC+10216 with ALMA. Also highlighted are ongoing laboratory studies of the silicon carbides SiC2 and SiCSi in their ground and excited vibrational states, and SiC3 in the ground vibrational state. Following the initial detection of SiC3 and SiCSi in the outer molecular envelope of IRC+10216, the laboratory spectroscopy was extended to higher frequency in support of the recent interferometric measurements. Thirty-two new millimeter-wave rotational transitions of SiCSi with J ≤ 48, Ka ≤ 3 and upper level energies Eu ≤ 484 K in the range from 178 - 391 GHz, and 35 new transitions of SiC3 with J ≤ 38, Ka ≤ 20 and Eu ≤ 875 K between 315 and 440 GHz were measured in the laboratory. In addition five to six rotational transitions in one quanta of each of the three fundamental vibrational modes of SiCSi, and the two lowest rotational transitions in the previously unexplored C-C stretching mode (ν 1) of SiCC were measured in the normal and doubly substituted 13C isotopic species.
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Affiliation(s)
- Michael C. McCarthy
- Harvard-Smithsonian Center for Astrophysics, 60 Garden St., Cambridge, MA 02138, U.S.A
| | - Carl A. Gottlieb
- Harvard-Smithsonian Center for Astrophysics, 60 Garden St., Cambridge, MA 02138, U.S.A
| | - Jose Cernicharo
- Group of Molecular Astrophysics, IFF-CSIC. C/Serrano 121, 28006 Madrid, Spain
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Cernicharo J, Guélin M, Agúndez M, Pardo JR, Massalkhi S, Fonfría JP, Velilla Prieto L, Quintana-Lacaci G, Marcelino N, Marka C, Navarro S, Kramer C. IRC +10216 as a spectroscopic laboratory: improved rotational constants for SiC 2, its isotopologues, and Si 2C. ASTRONOMY AND ASTROPHYSICS 2018; 618:A4. [PMID: 30429616 PMCID: PMC6231541 DOI: 10.1051/0004-6361/201833335] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
Abstract
This work presents a detailed analysis of the laboratory and astrophysical spectral data available for 28SiC2, 29SiC2,30SiC2, Si13CC, and Si2C. New data on the rotational lines of these species between 70 and 350 GHz have been obtained with high spectral resolution (195 kHz) with the IRAM 30m telescope in the direction of the circumstellar envelope IRC +10216. Frequency measurements can reach an accuracy of 50 kHz for features observed with a good signal to noise ratio. From the observed astrophysical lines and the available laboratory data new rotational and centrifugal distortion constants have been derived for all the isotopologues of SiC2, allowing to predict their spectrum with high accuracy in the millimeter and submillimeter domains. Improved rotational and centrifugal distortion constants have also been obtained for disilicon carbide, Si2C. This work shows that observations of IRC +10216 taken with the IRAM 30m telescope, with a spectral resolution of 195 kHz, can be used for any molecular species detected in this source to derive, or improve, its rotational constants. Hence, IRC +10216 in addition to be one the richest sources in molecular species in the sky, can also be used as a state-of-the-art spectroscopy laboratory in the millimeter and submillimeter domains.
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Affiliation(s)
- J. Cernicharo
- Group of Molecular Astrophysics, Instituto de Física Fundamental, CSIC, C/ Serrano 123, E-28006, Madrid, Spain
| | - M. Guélin
- Institut de Radioastronomie Millimétrique, 300 rue de la Piscine, F-38406, Saint Martin d'Hères, France
| | - M. Agúndez
- Group of Molecular Astrophysics, Instituto de Física Fundamental, CSIC, C/ Serrano 123, E-28006, Madrid, Spain
| | - J. R. Pardo
- Group of Molecular Astrophysics, Instituto de Física Fundamental, CSIC, C/ Serrano 123, E-28006, Madrid, Spain
| | - S. Massalkhi
- Group of Molecular Astrophysics, Instituto de Física Fundamental, CSIC, C/ Serrano 123, E-28006, Madrid, Spain
| | - J. P. Fonfría
- Group of Molecular Astrophysics, Instituto de Física Fundamental, CSIC, C/ Serrano 123, E-28006, Madrid, Spain
| | - L. Velilla Prieto
- Group of Molecular Astrophysics, Instituto de Física Fundamental, CSIC, C/ Serrano 123, E-28006, Madrid, Spain
| | - G. Quintana-Lacaci
- Group of Molecular Astrophysics, Instituto de Física Fundamental, CSIC, C/ Serrano 123, E-28006, Madrid, Spain
| | - N. Marcelino
- Group of Molecular Astrophysics, Instituto de Física Fundamental, CSIC, C/ Serrano 123, E-28006, Madrid, Spain
| | - C. Marka
- Instituto de Radioastronomía Milimétrica, Avenida Divina Pastora 7, E-18012, Granada, Spain
| | - S. Navarro
- Instituto de Radioastronomía Milimétrica, Avenida Divina Pastora 7, E-18012, Granada, Spain
| | - C. Kramer
- Instituto de Radioastronomía Milimétrica, Avenida Divina Pastora 7, E-18012, Granada, Spain
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11
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Zanchet A, Roncero O, Agúndez M, Cernicharo J. Formation and Destruction of SiS in Space. THE ASTROPHYSICAL JOURNAL 2018; 862:38. [PMID: 30190625 PMCID: PMC6122588 DOI: 10.3847/1538-4357/aaccff] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
The presence of SiS in space seems to be restricted to a few selected types of astronomical environments. It is long known to be present in circumstellar envelopes around evolved stars and it has also been detected in a handful of star-forming regions with evidence of outflows, like Sgr B2, Orion KL and more recently L1157-B1. The kinetics of reactions involving SiS is very poorly known and here we revisit the chemistry of SiS in space by studying some potentially important reactions of formation and destruction of this molecule. We calculated ab initio potential energy surfaces of the SiOS system and computed rate coefficients in the temperature range 50-2500 K for the reaction of destruction of SiS, in collisions with atomic O, and of its formation, through the reaction between Si and SO. We find that both reactions are rapid, with rate coefficients of a few times 10-10 cm3 s-1, almost independent of temperature. In the reaction between Si and SO, SiO production is 5-7 times more efficient than SiS formation. The reaction of SiS with O atoms can play an important role in destroying SiS in envelopes around evolved stars. We built a simple chemical model of a postshock gas to study the chemistry of SiS in protostellar outflows and we found that SiS forms with a lower abundance and later than SiO, that SiS is efficiently destroyed through reaction with O, and that the main SiS-forming reactions are Si + SO and Si + SO2.
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Affiliation(s)
- Alexandre Zanchet
- Instituto de Física Fundamental, CSIC, C/Serrano 123, E-28006 Madrid, Spain
| | - Octavio Roncero
- Instituto de Física Fundamental, CSIC, C/Serrano 123, E-28006 Madrid, Spain
| | - Marcelino Agúndez
- Instituto de Física Fundamental, CSIC, C/Serrano 123, E-28006 Madrid, Spain
| | - José Cernicharo
- Instituto de Física Fundamental, CSIC, C/Serrano 123, E-28006 Madrid, Spain
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12
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Fonfría JP, Fernández-López M, Pardo JR, Agúndez M, Sánchez Contreras C, Velilla Prieto L, Cernicharo J, Santander-García M, Quintana-Lacaci G, Castro-Carrizo A, Curiel S. The Maser Emitting Structure and Time Variability of the SIS Lines J = 14 - 13 and 15 - 14 in IRC+10216. THE ASTROPHYSICAL JOURNAL 2018; 860:162. [PMID: 29977091 PMCID: PMC6029660 DOI: 10.3847/1538-4357/aac5e3] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
We present new high angular resolution interferometer observations of the υ = 0 J = 14 - 13 and 15 - 14 SiS lines towards IRC+10216, carried out with CARMA and ALMA. The maps, with angular resolutions of ≃ 0 ⋅ ″ 25 and 0 ⋅ ″ 55 , reveal (1) an extended, roughly uniform, and weak emission with a size of ≃ 0 ⋅ ″ 5 , (2) a component elongated approximately along the East-West direction peaking at ≃ 0 ⋅ ″ 13 and 0 ⋅ ″ 17 at both sides of the central star, and (3) two blue- and red-shifted compact components peaking around 0 ⋅ ″ 07 to the NW of the star. We have modeled the emission with a 3D radiation transfer code finding that the observations cannot be explained only by thermal emission. Several maser clumps and one arc-shaped maser feature arranged from 5 to 20R⋆ from the central star, in addition to a thin shell-like maser structure at ≃ 13R⋆ are required to explain the observations. This maser emitting set of structures accounts for 75% of the total emission while the other 25% is produced by thermally excited molecules. About 60% of the maser emission comes from the extended emission and the rest from the set of clumps and the arc. The analysis of a time monitoring of these and other SiS and 29SiS lines carried out with the IRAM 30 m telescope from 2015 to present suggests that the intensity of some spectral components of the maser emission strongly depends on the stellar pulsation while other components show a mild variability. This monitoring evidences a significant phase lag of ≃ 0.2 between the maser and NIR light-curves.
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Affiliation(s)
- J P Fonfría
- Molecular Astrophysics Group, Instituto de Ciencia de Materiales de Madrid, CSIC, C/ Sor Juana Inés de la Cruz, 3, Cantoblanco, 28049, Madrid (Spain)
- Molecular Astrophysics Group, Instituto de Física Fundamental, CSIC, C/ Serrano, 123, 28006, Madrid (Spain)
| | - M Fernández-López
- Instituto Argentino de Radioastronomía, CCT-La Plata (CONICET), C.C.5, 1894, Villa Elisa (Argentina)
| | - J R Pardo
- Molecular Astrophysics Group, Instituto de Ciencia de Materiales de Madrid, CSIC, C/ Sor Juana Inés de la Cruz, 3, Cantoblanco, 28049, Madrid (Spain)
- Molecular Astrophysics Group, Instituto de Física Fundamental, CSIC, C/ Serrano, 123, 28006, Madrid (Spain)
| | - M Agúndez
- Molecular Astrophysics Group, Instituto de Ciencia de Materiales de Madrid, CSIC, C/ Sor Juana Inés de la Cruz, 3, Cantoblanco, 28049, Madrid (Spain)
- Molecular Astrophysics Group, Instituto de Física Fundamental, CSIC, C/ Serrano, 123, 28006, Madrid (Spain)
| | - C Sánchez Contreras
- Department of Astrophysics, Astrobiology Center (CSIC-INTA), Postal address: ESAC campus, P.O. Box 78, E-28691, Villanueva de la Canãda, Madrid (Spain)
| | - L Velilla Prieto
- Molecular Astrophysics Group, Instituto de Ciencia de Materiales de Madrid, CSIC, C/ Sor Juana Inés de la Cruz, 3, Cantoblanco, 28049, Madrid (Spain)
- Molecular Astrophysics Group, Instituto de Física Fundamental, CSIC, C/ Serrano, 123, 28006, Madrid (Spain)
| | - J Cernicharo
- Molecular Astrophysics Group, Instituto de Ciencia de Materiales de Madrid, CSIC, C/ Sor Juana Inés de la Cruz, 3, Cantoblanco, 28049, Madrid (Spain)
- Molecular Astrophysics Group, Instituto de Física Fundamental, CSIC, C/ Serrano, 123, 28006, Madrid (Spain)
| | - M Santander-García
- Observatorio Astronómico Nacional, OAN-IGN, Alfonso XII, 3, E-28014, Madrid (Spain)
| | - G Quintana-Lacaci
- Molecular Astrophysics Group, Instituto de Ciencia de Materiales de Madrid, CSIC, C/ Sor Juana Inés de la Cruz, 3, Cantoblanco, 28049, Madrid (Spain)
- Molecular Astrophysics Group, Instituto de Física Fundamental, CSIC, C/ Serrano, 123, 28006, Madrid (Spain)
| | - A Castro-Carrizo
- Institut de Radioastronomie Millimétrique, 300 Rue de la Piscine, 38406 Saint-Martin d'Hères (France)
| | - S Curiel
- Departamento de Astrofísica Teórica, Instituto de Astronomía, Universidad Nacional Autónoma de México, Ciudad Universitaria, 04510, Mexico City (Mexico)
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13
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Massalkhi S, Agúndez M, Cernicharo J, Velilla Prieto L, Goicoechea JR, Quintana-Lacaci G, Fonfría JP, Alcolea J, Bujarrabal V. The Abundance of SiC 2 in Carbon Star Envelopes: Evidence that SiC 2 is a gas-phase precursor of SiC dust. ASTRONOMY AND ASTROPHYSICS 2018; 611:A29. [PMID: 29628518 PMCID: PMC5884425 DOI: 10.1051/0004-6361/201732038] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/01/2023]
Abstract
CONTEXT Silicon carbide dust is ubiquitous in circumstellar envelopes around C-rich AGB stars. However, the main gas-phase precursors leading to the formation of SiC dust have not yet been identified. The most obvious candidates among the molecules containing an Si-C bond detected in C-rich AGB stars are SiC2, SiC, and Si2C. To date, the ring molecule SiC2 has been observed in a handful of evolved stars, while SiC and Si2C have only been detected in the C-star envelope IRC +10216. AIMS We aim to study how widespread and abundant SiC2, SiC, and Si2C are in envelopes around C-rich AGB stars and whether or not these species play an active role as gas-phase precursors of silicon carbide dust in the ejecta of carbon stars. METHODS We carried out sensitive observations with the IRAM 30m telescope of a sample of 25 C-rich AGB stars to search for emission lines of SiC2, SiC, and Si2C in the λ 2 mm band. We performed non-LTE excitation and radiative transfer calculations based on the LVG method to model the observed lines of SiC2 and to derive SiC2 fractional abundances in the observed envelopes. RESULTS We detect SiC2 in most of the sources, SiC in about half of them, and do not detect Si2C in any source, at the exception of IRC +10216. Most of these detections are reported for the first time in this work. We find a positive correlation between the SiC and SiC2 line emission, which suggests that both species are chemically linked, the SiC radical probably being the photodissociation product of SiC2 in the external layer of the envelope. We find a clear trend in which the denser the envelope, the less abundant SiC2 is. The observed trend is interpreted as an evidence of efficient incorporation of SiC2 onto dust grains, a process which is favored at high densities owing to the higher rate at which collisions between particles take place. CONCLUSIONS The observed behavior of a decline in the SiC2 abundance with increasing density strongly suggests that SiC2 is an important gas-phase precursor of SiC dust in envelopes around carbon stars.
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Affiliation(s)
- Sarah Massalkhi
- Grupo de Astrofísica Molecular, Instituto de Ciencia de Materiales de Madrid, CSIC, C/ Sor Juana Inés de la Cruz 3, 28049, Cantoblanco, Spain
| | - M Agúndez
- Grupo de Astrofísica Molecular, Instituto de Ciencia de Materiales de Madrid, CSIC, C/ Sor Juana Inés de la Cruz 3, 28049, Cantoblanco, Spain
| | - J Cernicharo
- Grupo de Astrofísica Molecular, Instituto de Ciencia de Materiales de Madrid, CSIC, C/ Sor Juana Inés de la Cruz 3, 28049, Cantoblanco, Spain
| | - L Velilla Prieto
- Grupo de Astrofísica Molecular, Instituto de Ciencia de Materiales de Madrid, CSIC, C/ Sor Juana Inés de la Cruz 3, 28049, Cantoblanco, Spain
| | - J R Goicoechea
- Grupo de Astrofísica Molecular, Instituto de Ciencia de Materiales de Madrid, CSIC, C/ Sor Juana Inés de la Cruz 3, 28049, Cantoblanco, Spain
| | - G Quintana-Lacaci
- Grupo de Astrofísica Molecular, Instituto de Ciencia de Materiales de Madrid, CSIC, C/ Sor Juana Inés de la Cruz 3, 28049, Cantoblanco, Spain
| | - J P Fonfría
- Grupo de Astrofísica Molecular, Instituto de Ciencia de Materiales de Madrid, CSIC, C/ Sor Juana Inés de la Cruz 3, 28049, Cantoblanco, Spain
| | - J Alcolea
- Observatorio Astronómico Nacional (IGN), C/ Alfonso XII 3, 28014, Madrid, Spain
| | - V Bujarrabal
- Observatorio Astronómico Nacional (IGN), Apartado de Correos 112, 28803, Alcalá de Henares, Madrid, Spain
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14
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Quintana-Lacaci G, Cernicharo J, Velilla Prieto L, Agúndez M, Castro-Carrizo A, Fonfría JP, Massalkhi S, Pardo JR. Clues to NaCN formation. ASTRONOMY AND ASTROPHYSICS 2017; 607:L5. [PMID: 29151609 PMCID: PMC5687569 DOI: 10.1051/0004-6361/201732015] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
CONTEXT ALMA is providing us essential information on where certain molecules form. Observing where these molecules emission arises from, the physical conditions of the gas, and how this relates with the presence of other species allows us to understand the formation of many species, and to significantly improve our knowledge of the chemistry that occurs in the space. AIMS We studied the molecular distribution of NaCN around IRC +10216, a molecule detected previously, but whose origin is not clear. High angular resolution maps allow us to model the abundance distribution of this molecule and check suggested formation paths. METHODS We modeled the emission of NaCN assuming local thermal equilibrium (LTE) conditions. These profiles were fitted to azimuthal averaged intensity profiles to obtain an abundance distribution of NaCN. RESULTS We found that the presence of NaCN seems compatible with the presence of CN, probably as a result of the photodissociation of HCN, in the inner layers of the ejecta of IRC +10216. However, similar as for CH3CN, current photochemical models fail to reproduce this CN reservoir. We also found that the abundance peak of NaCN appears at a radius of 3 × 1015cm, approximately where the abundance of NaCl, suggested to be the parent species, starts to decay. However, the abundance ratio shows that the NaCl abundance is lower than that obtained for NaCN. We expect that the LTE assumption might result in NaCN abundances higher than the real ones. Updated photochemical models, collisional rates, and reaction rates are essential to determine the possible paths of the NaCN formation.
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Affiliation(s)
- G Quintana-Lacaci
- Instituto de Ciencia de Materiales de Madrid, Sor Juana Inés de la Cruz, 3, Cantoblanco, 28049 Madrid, Spain
| | - J Cernicharo
- Instituto de Ciencia de Materiales de Madrid, Sor Juana Inés de la Cruz, 3, Cantoblanco, 28049 Madrid, Spain
| | - L Velilla Prieto
- Instituto de Ciencia de Materiales de Madrid, Sor Juana Inés de la Cruz, 3, Cantoblanco, 28049 Madrid, Spain
| | - M Agúndez
- Instituto de Ciencia de Materiales de Madrid, Sor Juana Inés de la Cruz, 3, Cantoblanco, 28049 Madrid, Spain
| | - A Castro-Carrizo
- Institut de RadioAstronomie Millimétrique, 300 rue de la Piscine, 38406 Saint Martin dH́éres, France
| | - J P Fonfría
- Instituto de Ciencia de Materiales de Madrid, Sor Juana Inés de la Cruz, 3, Cantoblanco, 28049 Madrid, Spain
| | - S Massalkhi
- Instituto de Ciencia de Materiales de Madrid, Sor Juana Inés de la Cruz, 3, Cantoblanco, 28049 Madrid, Spain
| | - J R Pardo
- Instituto de Ciencia de Materiales de Madrid, Sor Juana Inés de la Cruz, 3, Cantoblanco, 28049 Madrid, Spain
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15
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Cernicharo J, Agúndez M, Velilla Prieto L, Guélin M, Pardo JR, Kahane C, Marka C, Kramer C, Navarro S, Quintana-Lacaci G, Fonfría JP, Marcelino N, Tercero B, Moreno E, Massalkhi S, Santander-García M, McCarthy MC, Gottlieb CA, Alonso JL. Discovery of methyl silane and confirmation of silyl cyanide in IRC +10216. ASTRONOMY AND ASTROPHYSICS 2017; 606:L5. [PMID: 29142328 PMCID: PMC5683346 DOI: 10.1051/0004-6361/201731672] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/01/2023]
Abstract
We report the discovery in space of methyl silane, CH3SiH3, from observations of ten rotational transitions between 80 and 350 GHz (Ju from 4 to 16) with the IRAM 30 m radio telescope. The molecule was observed in the envelope of the C-star IRC +10216. The observed profiles and our models for the expected emission of methyl silane suggest that the it is formed in the inner zones of the circumstellar envelope, 1-40 R*, with an abundance of (0.5-1) × 10-8 relative to H2. We also observed several rotational transitions of silyl cyanide (SiH3CN), confirming its presence in IRC +10216 in particular, and in space in general. Our models indicate that silyl cyanide is also formed in the inner regions of the envelope, around 20 R*, with an abundance relative to H2 of 6×10-10. The possible formation mechanisms of both species are discussed. We also searched for related chemical species but only upper limits could be obtained.
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Affiliation(s)
- J Cernicharo
- Group of Molecular Astrophysics, ICMM, CSIC, C/ Sor Juana Inés de La Cruz 3, 28049 Madrid, Spain
| | - M Agúndez
- Group of Molecular Astrophysics, ICMM, CSIC, C/ Sor Juana Inés de La Cruz 3, 28049 Madrid, Spain
| | - L Velilla Prieto
- Group of Molecular Astrophysics, ICMM, CSIC, C/ Sor Juana Inés de La Cruz 3, 28049 Madrid, Spain
| | - M Guélin
- Institut de Radioastronomie Millimétrique, 300 rue de la Piscine, 38406 St-Martin d'Hères, France
| | - J R Pardo
- Group of Molecular Astrophysics, ICMM, CSIC, C/ Sor Juana Inés de La Cruz 3, 28049 Madrid, Spain
| | - C Kahane
- Université Grenoble Alpes, CNRS, IPAG, 38000 Grenoble, France
| | - C Marka
- Instituto de Radioastronomía Milimétrica, Av. Divina Pastora 7, Local 20, 18012 Granada, Spain
| | - C Kramer
- Instituto de Radioastronomía Milimétrica, Av. Divina Pastora 7, Local 20, 18012 Granada, Spain
| | - S Navarro
- Instituto de Radioastronomía Milimétrica, Av. Divina Pastora 7, Local 20, 18012 Granada, Spain
| | - G Quintana-Lacaci
- Group of Molecular Astrophysics, ICMM, CSIC, C/ Sor Juana Inés de La Cruz 3, 28049 Madrid, Spain
| | - J P Fonfría
- Group of Molecular Astrophysics, ICMM, CSIC, C/ Sor Juana Inés de La Cruz 3, 28049 Madrid, Spain
| | - N Marcelino
- Group of Molecular Astrophysics, ICMM, CSIC, C/ Sor Juana Inés de La Cruz 3, 28049 Madrid, Spain
| | - B Tercero
- Group of Molecular Astrophysics, ICMM, CSIC, C/ Sor Juana Inés de La Cruz 3, 28049 Madrid, Spain
| | - E Moreno
- Group of Molecular Astrophysics, ICMM, CSIC, C/ Sor Juana Inés de La Cruz 3, 28049 Madrid, Spain
| | - S Massalkhi
- Group of Molecular Astrophysics, ICMM, CSIC, C/ Sor Juana Inés de La Cruz 3, 28049 Madrid, Spain
| | - M Santander-García
- Group of Molecular Astrophysics, ICMM, CSIC, C/ Sor Juana Inés de La Cruz 3, 28049 Madrid, Spain
| | - M C McCarthy
- Harvard-Smithsonian Center for Astrophysics, Cambridge, MA 02138, and School of Engineering & Applied Sciences, Harvard University, Cambridge, MA 02138, USA
| | - C A Gottlieb
- Harvard-Smithsonian Center for Astrophysics, Cambridge, MA 02138, and School of Engineering & Applied Sciences, Harvard University, Cambridge, MA 02138, USA
| | - J L Alonso
- Grupo de Espectroscopía Molecular (GEM), Edificio Quifima, Área de Química-Física, Laboratorios de Espectroscopía y Bioespectroscopía, Parque Científico UVa, Unidad Asociada CSIC, Universidad de Valladolid, 47011 Valladolid, Spain
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16
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Agúndez M, Cernicharo J, Quintana-Lacaci G, Castro-Carrizo A, Velilla Prieto L, Marcelino N, Guélin M, Joblin C, Martín-Gago JA, Gottlieb CA, Patel NA, McCarthy MC. The growth of carbon chains in IRC +10216 mapped with ALMA. ASTRONOMY AND ASTROPHYSICS 2017; 601:A4. [PMID: 28469283 PMCID: PMC5405872 DOI: 10.1051/0004-6361/201630274] [Citation(s) in RCA: 25] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
Abstract
Linear carbon chains are common in various types of astronomical molecular sources. Possible formation mechanisms involve both bottom-up and top-down routes. We have carried out a combined observational and modeling study of the formation of carbon chains in the C-star envelope IRC +10216, where the polymerization of acetylene and hydrogen cyanide induced by ultraviolet photons can drive the formation of linear carbon chains of increasing length. We have used ALMA to map the emission of λ 3 mm rotational lines of the hydrocarbon radicals C2H, C4H, and C6H, and the CN-containing species CN, C3N, HC3N, and HC5N with an angular resolution of ~1″. The spatial distribution of all these species is a hollow, 5-10″ wide, spherical shell located at a radius of 10-20″ from the star, with no appreciable emission close to the star. Our observations resolve the broad shell of carbon chains into thinner sub-shells which are 1-2″ wide and not fully concentric, indicating that the mass loss process has been discontinuous and not fully isotropic. The radial distributions of the species mapped reveal subtle differences: while the hydrocarbon radicals have very similar radial distributions, the CN-containing species show more diverse distributions, with HC3N appearing earlier in the expansion and the radical CN extending later than the rest of the species. The observed morphology can be rationalized by a chemical model in which the growth of polyynes is mainly produced by rapid gas-phase chemical reactions of C2H and C4H radicals with unsaturated hydrocarbons, while cyanopolyynes are mainly formed from polyynes in gas-phase reactions with CN and C3N radicals.
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Affiliation(s)
- M Agúndez
- Instituto de Ciencia de Materiales de Madrid, CSIC, C/ Sor Juana Inés de la Cruz 3, 28049 Cantoblanco, Spain
| | - J Cernicharo
- Instituto de Ciencia de Materiales de Madrid, CSIC, C/ Sor Juana Inés de la Cruz 3, 28049 Cantoblanco, Spain
| | - G Quintana-Lacaci
- Instituto de Ciencia de Materiales de Madrid, CSIC, C/ Sor Juana Inés de la Cruz 3, 28049 Cantoblanco, Spain
| | - A Castro-Carrizo
- Institut de Radioastronomie Millimétrique, 300 rue de la Piscine, 38406 St. Martin d'Héres, France
| | - L Velilla Prieto
- Instituto de Ciencia de Materiales de Madrid, CSIC, C/ Sor Juana Inés de la Cruz 3, 28049 Cantoblanco, Spain
| | - N Marcelino
- Instituto de Ciencia de Materiales de Madrid, CSIC, C/ Sor Juana Inés de la Cruz 3, 28049 Cantoblanco, Spain
| | - M Guélin
- Institut de Radioastronomie Millimétrique, 300 rue de la Piscine, 38406 St. Martin d'Héres, France
| | - C Joblin
- Université de Toulouse, UPS-OMS, IRAP, 31000 Toulouse, France
- CNRS, IRAP, 9 Av. Colonel Roche, BP 44346, 31028 Toulouse Cedex 4, France
| | - J A Martín-Gago
- Instituto de Ciencia de Materiales de Madrid, CSIC, C/ Sor Juana Inés de la Cruz 3, 28049 Cantoblanco, Spain
| | - C A Gottlieb
- Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138, USA
| | - N A Patel
- Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138, USA
| | - M C McCarthy
- Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138, USA
- School of Engineering and Applied Sciences, Harvard University, Cambridge, MA 02138, USA
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17
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Cabezas C, Cernicharo J, Quintana-Lacaci G, Peña I, Agundez M, Prieto LV, Castro-Carrizo A, Zuñiga J, Bastida A, Alonso JL, Requena A. High-Resolution Rotational Spectrum, Dunham Coefficients, and Potential Energy Function of NaCl. THE ASTROPHYSICAL JOURNAL 2016; 825:150. [PMID: 27733778 PMCID: PMC5056638 DOI: 10.3847/0004-637x/825/2/150] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
We report laboratory spectroscopy for the first time of the J = 1-0 and J = 2-1 lines of Na35Cl and Na37Cl in several vibrational states. The hyperfine structure has been resolved in both transitions for all vibrational levels, which permit us to predict with high accuracy the hyperfine splitting of the rotational transitions of the two isotopologues at higher frequencies. The new data have been merged with all previous works at microwave, millimeter, and infrared wavelengths and fitted to a series of mass-independent Dunham parameters and to a potential energy function. The obtained parameters have been used to compute a new dipole moment function, from which the dipole moment for infrared transitions up to Δv = 8 has been derived. Frequency and intensity predictions are provided for all rovibrational transitions up to J = 150 and v = 8, from which the ALMA data of evolved stars can be modeled and interpreted.
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Affiliation(s)
- C Cabezas
- Grupo de Espectroscopía Molecular, Edificio Quifima, Laboratorios de Espectroscopía y Bioespectroscopía, Unidad asociada CSIC, Parque científico Uva, Universidad de Valladolid, Paseo de Belén 5, E-47011, Valladolid, Spain
| | - J Cernicharo
- Group of Molecular Astrophysics, ICMM, CSIC. C/Sor Juana Inés de la Cruz 3, E-28049 Cantoblanco, Madrid, Spain
| | - G Quintana-Lacaci
- Group of Molecular Astrophysics, ICMM, CSIC. C/Sor Juana Inés de la Cruz 3, E-28049 Cantoblanco, Madrid, Spain
| | - I Peña
- Grupo de Espectroscopía Molecular, Edificio Quifima, Laboratorios de Espectroscopía y Bioespectroscopía, Unidad asociada CSIC, Parque científico Uva, Universidad de Valladolid, Paseo de Belén 5, E-47011, Valladolid, Spain
| | - M Agundez
- Group of Molecular Astrophysics, ICMM, CSIC. C/Sor Juana Inés de la Cruz 3, E-28049 Cantoblanco, Madrid, Spain
| | - L Velilla Prieto
- Group of Molecular Astrophysics, ICMM, CSIC. C/Sor Juana Inés de la Cruz 3, E-28049 Cantoblanco, Madrid, Spain
| | - A Castro-Carrizo
- Institut de Radioastronomie Millimétrique, 300 rue de la la Piscine, F-38406, Saint Martin d'Hères, France
| | - J Zuñiga
- Universidad de Murcia. Faculdad de Química, Dpto. de Química-Física, Campus Espinardo E-30100, Murcia, Spain
| | - A Bastida
- Universidad de Murcia. Faculdad de Química, Dpto. de Química-Física, Campus Espinardo E-30100, Murcia, Spain
| | - J L Alonso
- Grupo de Espectroscopía Molecular, Edificio Quifima, Laboratorios de Espectroscopía y Bioespectroscopía, Unidad asociada CSIC, Parque científico Uva, Universidad de Valladolid, Paseo de Belén 5, E-47011, Valladolid, Spain
| | - A Requena
- Universidad de Murcia. Faculdad de Química, Dpto. de Química-Física, Campus Espinardo E-30100, Murcia, Spain
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18
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Quintana-Lacaci G, Cernicharo J, Agúndez M, Prieto LV, Castro-Carrizo A, Marcelino N, Cabezas C, Peña I, Alonso JL, Zúñiga J, Requena A, Bastida A, Kalugina Y, Lique F, Guélin M. Hints of a rotating spiral structure in the innermost regions around IRC +10216. THE ASTROPHYSICAL JOURNAL 2016; 818:192. [PMID: 26997665 PMCID: PMC4797422 DOI: 10.3847/0004-637x/818/2/192] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/01/2023]
Abstract
The Atacama Large Millimeter/submillimeter Array (ALMA) is allowing us to study the innermost regions of the circumstellar envelopes of evolved stars with un-precedented precision and sensitivity. Key processes in the ejection of matter and dust from these objects occur in their inner zones. In this work, we present sub-arcsecond interferometric maps of transitions of metal-bearing molecules towards the prototypical C-rich evolved star IRC +10216. While Al-bearing molecules seem to be present as a roughly spherical shell, the molecular emission from the salts NaCl and KCl presents an elongation in the inner regions, with a central minimum. In order to accurately analyze the emission from the NaCl rotational lines, we present new calculations of the collisional rates for this molecule based on new spectroscopic constants. The most plausible interpretation for the spatial distribution of the salts is a spiral with a NaCl mass of 0.08M☉. Alternatively, a torus of gas and dust would result in similar structures as those observed. From the torus scenario we derive a mass of ~ 1.1 × 10-4M☉. In both cases, the spiral and the torus, the NaCl structure presents an inner minimum of 27 AU. In the case of the torus, the outer radius is 73 AU. The kinematics of both the spiral and the torus suggests that they are slowly expanding and rotating. Alternative explanations for the presence of the elongation are explored. The presence of these features only in KCl and NaCl might be a result of their comparatively high dipole moment with respect to the Al-bearing species.
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Affiliation(s)
- G Quintana-Lacaci
- Group of Molecular Astrophysics. ICMM, CSIC. C/ Sor Juana Inés de la Cruz 3, 28049 Cantoblanco, Madrid, Spain
| | - J Cernicharo
- Group of Molecular Astrophysics. ICMM, CSIC. C/ Sor Juana Inés de la Cruz 3, 28049 Cantoblanco, Madrid, Spain
| | - M Agúndez
- Group of Molecular Astrophysics. ICMM, CSIC. C/ Sor Juana Inés de la Cruz 3, 28049 Cantoblanco, Madrid, Spain
| | - L Velilla Prieto
- 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
| | - A Castro-Carrizo
- Institut de Radioastronomie Millimétrique. 300 rue de la la Piscine, F-38406, Saint Martin d'Hères, France
| | - N Marcelino
- INAF, Istituto di Radioastronomia, via P. Gobetti 101, 40129, Bologna, Italy
| | - C Cabezas
- Grupo de Espectroscopía Molecular, Edificio Quifima, Laboratorios de Espectroscopía y Bioe-spectroscopía. Unidad asociada CSIC, Parque científico Uva, Universidad de Valladolid, Paseo de Belén 5, E-47011, Valladolid, Spain
| | - I Peña
- Grupo de Espectroscopía Molecular, Edificio Quifima, Laboratorios de Espectroscopía y Bioe-spectroscopía. Unidad asociada CSIC, Parque científico Uva, Universidad de Valladolid, Paseo de Belén 5, E-47011, Valladolid, Spain
| | - J L Alonso
- Grupo de Espectroscopía Molecular, Edificio Quifima, Laboratorios de Espectroscopía y Bioe-spectroscopía. Unidad asociada CSIC, Parque científico Uva, Universidad de Valladolid, Paseo de Belén 5, E-47011, Valladolid, Spain
| | - J Zúñiga
- Universidad de Murcia. Faculdad de Química. Dpto. de Química-Física. Campus Espinardo E-30100, Murcia, Spain
| | - A Requena
- Universidad de Murcia. Faculdad de Química. Dpto. de Química-Física. Campus Espinardo E-30100, Murcia, Spain
| | - A Bastida
- Universidad de Murcia. Faculdad de Química. Dpto. de Química-Física. Campus Espinardo E-30100, Murcia, Spain
| | - Y Kalugina
- LOMC-UMR 6294, CNRS-Université du Havre, 25 rue Philippe Lebon, BP. 1123, 76063 Le Havre cedex, France ; Department of Optics and Spectroscopy, Tomsk State University, 36 Lenin av., Tomsk 634050, Russia
| | - F Lique
- LOMC-UMR 6294, CNRS-Université du Havre, 25 rue Philippe Lebon, BP. 1123, 76063 Le Havre cedex, France
| | - M Guélin
- 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
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Agúndez M, Cernicharo J, Quintana-Lacaci G, Prieto LV, Castro-Carrizo A, Marcelino N, Guélin M. THE PECULIAR DISTRIBUTION OF CH 3CN IN IRC +10216 SEEN BY ALMA. THE ASTROPHYSICAL JOURNAL 2015; 814:143. [PMID: 26709313 PMCID: PMC4688943 DOI: 10.1088/0004-637x/814/2/143] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
Abstract
IRC +10216 is a circumstellar envelope around a carbon-rich evolved star which contains a large variety of molecules. According to interferometric observations, molecules are distributed either concentrated around the central star or as a hollow shell with a radius of ~15″. We present ALMA Cycle 0 band 6 observations of the J = 14 - 13 rotational transition of CH3CN in IRC +10216, obtained with an angular resolution of [Formula: see text]. The bulk of the emission is distributed as a hollow shell located at just ~2″ from the star, with a void of emission in the central region up to a radius of ~1″. This spatial distribution is markedly different from those found to date in this source for other molecules. Our analysis indicate that methyl cyanide is not formed neither in the stellar photosphere nor far in the outer envelope, but at radial distances as short as 1-2″, reaching a maximum abundance of ~ 0.02 molecules cm-3 at 2″ from the star. Standard chemical models of IRC +10216 predict that the bulk of CH3CN molecules should be present at a radius of ~ 15″, where other species such as polyyne radicals and cyanopolyynes are observed, with an additional inner component within 1″ from the star. The non-uniform structure of the circumstellar envelope and grain surface processes are discussed as possible causes of the peculiar distribution of methyl cyanide in IRC +10216.
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Affiliation(s)
- M Agúndez
- Instituto de Ciencia de Materiales de Madrid, CSIC, C/ Sor Juana Inés de la Cruz 3, 28049 Cantoblanco, Spain
| | - J Cernicharo
- Instituto de Ciencia de Materiales de Madrid, CSIC, C/ Sor Juana Inés de la Cruz 3, 28049 Cantoblanco, Spain
| | - G Quintana-Lacaci
- Instituto de Ciencia de Materiales de Madrid, CSIC, C/ Sor Juana Inés de la Cruz 3, 28049 Cantoblanco, Spain
| | - L Velilla Prieto
- Instituto de Ciencia de Materiales de Madrid, CSIC, C/ Sor Juana Inés de la Cruz 3, 28049 Cantoblanco, Spain
| | - A Castro-Carrizo
- Institut de Radioastronomie Millimétrique, 300 rue de la Piscine, 38406 St. Martin d'Héres, France
| | - N Marcelino
- INAF, Istituto di Radioastronomia, via Gobetti 101, 40129 Bologna, Italy
| | - M Guélin
- Institut de Radioastronomie Millimétrique, 300 rue de la Piscine, 38406 St. Martin d'Héres, France
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Fonfría JP, Cernicharo J, Richter MJ, Fernández-López M, Prieto LV, Lacy JH. The abundance of 28Si 32S, 29Si 32S, 28Si 34S, and 30Si 32S in the inner layers of the envelope of IRC+10216. MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY 2015; 453:439-449. [PMID: 26997679 PMCID: PMC4797415 DOI: 10.1093/mnras/stv1634] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/01/2023]
Abstract
We present high spectral resolution mid-IR observations of SiS towards the C-rich AGB star IRC+10216 carried out with the Texas Echelon-cross-Echelle Spectrograph mounted on the NASA Infrared Telescope Facility. We have identified 204 ro-vibrational lines of 28Si32S, 26 of 29Si32S, 20 of 28Si34S, and 15 of 30Si32S in the frequency range 720 - 790 cm-1. These lines belong to bands v = 1 - 0, 2 - 1, 3 - 2, 4-3, and 5-4, and involve rotational levels with Jlow ≲ 90. About 30 per cent of these lines are unblended or weakly blended and can be partially or entirely fitted with a code developed to model the mid-IR emission of a spherically symmetric circumstellar envelope composed of expanding gas and dust. The observed lines trace the envelope at distances to the star ≲ 35R⋆(≃ 0″.7). The fits are compatible with an expansion velocity of 1+2.5(r/R⋆ -1) km s-1 between 1 and 5R⋆, 11 km s-1 between 5 and 20R⋆, and 14.5 km s-1 outwards. The derived abundance profile of 28Si32S with respect to H2 is 4.9 × 10-6 between the stellar photosphere and 5R⋆, decreasing linearly down to 1.6 × 10-6 at 20R⋆ and to 1.3 × 10-6 at 50R⋆. 28Si32S seems to be rotationally under LTE in the region of the envelope probed with our observations and vibrationally out of LTE in most of it. There is a red-shifted emission excess in the 28Si32S lines of band v = 1 - 0 that cannot be found in the lines of bands v = 2 - 1, 3 - 2, 4 - 3, and 5 - 4. This excess could be explained by an enhancement of the vibrational temperature around 20R⋆ behind the star. The derived isotopic ratios 28Si/29Si, and 32S/34S are 17 and 14, compatible with previous estimates.
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Affiliation(s)
- J. P. Fonfría
- Departamento de Estrellas y Medio Interestelar, Instituto de Astronomía, UNAM, Ciudad Universitaria, 04510, Mexico City (Mexico)
| | - J. Cernicharo
- Grupo de Astrofísica Molecular, Instituto de Ciencia de Materiales de Madrid, CSIC, C/ Sor Juana Inés de la Cruz 3, 28049, Cantoblanco, Madrid (Spain)
| | - M. J. Richter
- Physics Dept. - UC Davis, One Shields Ave., Davis, CA 95616 (USA)
| | - M. Fernández-López
- Instituto Argentino de Radioastronomía, CCT-La Plata (CONICET), C.C.5, 1894, Villa Elisa (Argentina)
| | - L. Velilla Prieto
- Grupo de Astrofísica Molecular, Instituto de Ciencia de Materiales de Madrid, CSIC, C/ Sor Juana Inés de la Cruz 3, 28049, Cantoblanco, Madrid (Spain)
| | - J. H. Lacy
- Astronomy Dept., University of Texas, Austin, TX 78712 (USA)
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Cernicharo J, McCarthy MC, Gottlieb CA, Agúndez M, Velilla Prieto L, Baraban JH, Changala PB, Guélin M, Kahane C, Martin-Drumel MA, Patel NA, Reilly NJ, Stanton JF, Quintana-Lacaci G, Thorwirth S, Young KH. Discovery of SiCSi in IRC +10216: A missing link between gas and dust carriers of Si-C bonds. THE ASTROPHYSICAL JOURNAL. LETTERS 2015; 806:L3. [PMID: 26722621 PMCID: PMC4693961 DOI: 10.1088/2041-8205/806/1/l3] [Citation(s) in RCA: 62] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
We report the discovery in space of a disilicon species, SiCSi, from observations between 80 and 350 GHz with the IRAM 30m radio telescope. Owing to the close coordination between laboratory experiments and astrophysics, 112 lines have now been detected in the carbon-rich star CW Leo. The derived frequencies yield improved rotational and centrifugal distortion constants up to sixth order. From the line profiles and interferometric maps with the Submillimeter Array, the bulk of the SiCSi emission arises from a region of 6″ in radius. The derived abundance is comparable to that of SiC2. As expected from chemical equilibrium calculations, SiCSi and SiC2 are the most abundant species harboring a Si-C bond in the dust formation zone and certainly both play a key role in the formation of SiC dust grains.
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Affiliation(s)
- J Cernicharo
- Group of Molecular Astrophysics. ICMM. CSIC. C/Sor Juana Inés de La Cruz N3. E-28049, Madrid. Spain
| | - M C McCarthy
- Harvard-Smithsonian Center for Astrophysics, Cambridge, MA 02138, and School of Engineering & Applied Sciences, Harvard University, Cambridge, MA 02138
| | - C A Gottlieb
- Harvard-Smithsonian Center for Astrophysics, Cambridge, MA 02138, and School of Engineering & Applied Sciences, Harvard University, Cambridge, MA 02138
| | - M Agúndez
- Group of Molecular Astrophysics. ICMM. CSIC. C/Sor Juana Inés de La Cruz N3. E-28049, Madrid. Spain
| | - L Velilla Prieto
- Group of Molecular Astrophysics. ICMM. CSIC. C/Sor Juana Inés de La Cruz N3. E-28049, Madrid. Spain
| | - J H Baraban
- Department of Chemistry and Biochemistry, University of Colorado, Boulder, CO 80309
| | - P B Changala
- JILA, National Institute of Standards and Technology and University of Colorado, and Department of Physics, University of Colorado, Boulder, CO 80309
| | - M Guélin
- Institut de Radioastronomie Millimétrique, 300 rue de la Piscine, F-38406, St-Martin d'Hères, France
| | - C Kahane
- Universit Grenoble Alpes, IPAG, F-38000 Grenoble, France; CNRS, IPAG, F-38000 Grenoble, France
| | - M A Martin-Drumel
- Harvard-Smithsonian Center for Astrophysics, Cambridge, MA 02138, and School of Engineering & Applied Sciences, Harvard University, Cambridge, MA 02138
| | - N A Patel
- Harvard-Smithsonian Center for Astrophysics, Cambridge, MA 02138, and School of Engineering & Applied Sciences, Harvard University, Cambridge, MA 02138
| | - N J Reilly
- Harvard-Smithsonian Center for Astrophysics, Cambridge, MA 02138, and School of Engineering & Applied Sciences, Harvard University, Cambridge, MA 02138
| | - J F Stanton
- Institute for Theoretical Chemistry, Department of Chemistry, The University of Texas at Austin, Austin, TX 78712
| | - G Quintana-Lacaci
- Group of Molecular Astrophysics. ICMM. CSIC. C/Sor Juana Inés de La Cruz N3. E-28049, Madrid. Spain
| | - S Thorwirth
- I. Physikalisches Institut, Universität zu Köln, Zülpicher Str. 77, 50937 Köln, Germany
| | - K H Young
- Harvard-Smithsonian Center for Astrophysics, Cambridge, MA 02138, and School of Engineering & Applied Sciences, Harvard University, Cambridge, MA 02138
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