291 results on '"MOLECULAR astrophysics"'
Search Results
2. Interstellar Complex Organic Molecules in Solar-Type Star-Forming Regions: From Observations to Laboratory, Theoretical Computations and Models
- Author
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Ceccarelli, Cecilia, Mennella, Vito, editor, and Joblin, Christine, editor
- Published
- 2023
- Full Text
- View/download PDF
3. Proton and Electron Irradiations of CH 4 :H 2 O Mixed Ices.
- Author
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Mifsud, Duncan V., Herczku, Péter, Sulik, Béla, Juhász, Zoltán, Vajda, István, Rajta, István, Ioppolo, Sergio, Mason, Nigel J., Strazzulla, Giovanni, and Kaňuchová, Zuzana
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IRRADIATION ,GALACTIC cosmic rays ,IONIZING radiation ,COSMIC rays ,PROTONS ,ORGANIC chemistry ,SOLAR system ,ELECTRONS - Abstract
The organic chemistry occurring in interstellar environments may lead to the production of complex molecules that are relevant to the emergence of life. Therefore, in order to understand the origins of life itself, it is necessary to probe the chemistry of carbon-bearing molecules under conditions that simulate interstellar space. Several of these regions, such as dense molecular cores, are exposed to ionizing radiation in the form of galactic cosmic rays, which may act as an important driver of molecular destruction and synthesis. In this paper, we report the results of a comparative and systematic study of the irradiation of CH
4 :H2 O ice mixtures by 1 MeV protons and 2 keV electrons at 20 K. We demonstrate that our irradiations result in the formation of a number of new products, including both simple and complex daughter molecules such as C2 H6 , C3 H8 , C2 H2 , CH3 OH, CO, CO2 , and probably also H2 CO. A comparison of the different irradiation regimes has also revealed that proton irradiation resulted in a greater abundance of radiolytic daughter molecules compared to electron irradiation, despite a lower radiation dose having been administered. These results are important in the context of the radiation astrochemistry occurring within the molecular cores of dense interstellar clouds, as well as on outer Solar System objects. [ABSTRACT FROM AUTHOR]- Published
- 2023
- Full Text
- View/download PDF
4. Atomic and Molecular Radiative Processes : With Applications to Modern Spectroscopy and the Greenhouse Effect
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Vladimir Krainov, Boris M. Smirnov, Vladimir Krainov, and Boris M. Smirnov
- Subjects
- Electromagnetic interactions, Electromagnetic waves, Molecular astrophysics
- Abstract
This book describes selected problems in contemporary spectroscopy in the context of quantum mechanics and statistical physics. It focuses on elementary radiative processes involving atomic particles (atoms, molecules, ions), which include radiative transitions between discrete atomic states, the photoionization of atoms, photorecombination of electrons and ions, bremsstrahlung, photodissociation of molecules, and photoattachment of electrons to atoms. In addition to these processes, the transport of resonant radiation in atomic gases and propagation of infrared radiation in molecular gases are also considered. The book subsequently addresses applied problems such as optical pumping, cooling of gases via laser resonance radiation, light-induced drift of gas atoms, photoresonant plasma, reflection of radio waves from the ionosphere, and detection of submillimeter radiation using Rydberg atoms. Lastly, topical examples in atmospheric and climate change science are presented, such as lightning channel glowing, emission of the solar photosphere, and the greenhouse phenomenon in the atmospheres of the Earth and Venus. Along with researchers, both graduate and undergraduate students in atomic, molecular and atmospheric physics will find this book a useful and timely guide.
- Published
- 2019
5. Proton and Electron Irradiations of CH4:H2O Mixed Ices
- Author
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Duncan V. Mifsud, Péter Herczku, Béla Sulik, Zoltán Juhász, István Vajda, István Rajta, Sergio Ioppolo, Nigel J. Mason, Giovanni Strazzulla, and Zuzana Kaňuchová
- Subjects
astrochemistry ,molecular astrophysics ,radiation chemistry ,methane ice ,water ice ,Nuclear and particle physics. Atomic energy. Radioactivity ,QC770-798 - Abstract
The organic chemistry occurring in interstellar environments may lead to the production of complex molecules that are relevant to the emergence of life. Therefore, in order to understand the origins of life itself, it is necessary to probe the chemistry of carbon-bearing molecules under conditions that simulate interstellar space. Several of these regions, such as dense molecular cores, are exposed to ionizing radiation in the form of galactic cosmic rays, which may act as an important driver of molecular destruction and synthesis. In this paper, we report the results of a comparative and systematic study of the irradiation of CH4:H2O ice mixtures by 1 MeV protons and 2 keV electrons at 20 K. We demonstrate that our irradiations result in the formation of a number of new products, including both simple and complex daughter molecules such as C2H6, C3H8, C2H2, CH3OH, CO, CO2, and probably also H2CO. A comparison of the different irradiation regimes has also revealed that proton irradiation resulted in a greater abundance of radiolytic daughter molecules compared to electron irradiation, despite a lower radiation dose having been administered. These results are important in the context of the radiation astrochemistry occurring within the molecular cores of dense interstellar clouds, as well as on outer Solar System objects.
- Published
- 2023
- Full Text
- View/download PDF
6. Systems Astrochemistry: A New Doctrine for Experimental Studies
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Nigel J. Mason, Perry A. Hailey, Duncan V. Mifsud, and James S. Urquhart
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astrochemistry ,interstellar chemistry ,molecular astrophysics ,systems science ,systems astrochemistry ,design of experiments ,Astronomy ,QB1-991 ,Geophysics. Cosmic physics ,QC801-809 - Abstract
Laboratory experiments play a key role in deciphering the chemistry of the interstellar medium (ISM) and the formation of complex organic molecules (COMs) relevant to life. To date, however, most studies in experimental astrochemistry have made use of a reductionist approach to experimental design in which chemical responses to variations in a single parameter are investigated while all other parameters are held constant. Although such work does afford insight into the chemistry of the ISM, it is likely that several important points (e.g., the possible influence of experimental parameter interaction) remain ambiguous. In light of this, we propose the adoption of a new “systems astrochemistry” approach for experimental studies and present the basic tenants and advantages of this approach in this perspective article. Such an approach has already been used for some time now and to great effect in the field of prebiotic chemistry, and so we anticipate that its application to experimental astrochemistry will uncover new data hitherto unknown which could aid in better linking laboratory work to observations and models.
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- 2021
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7. A Dirty Window : Diffuse and Translucent Molecular Gas in the Interstellar Medium
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Loris Magnani, Steven N. Shore, Loris Magnani, and Steven N. Shore
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- Interstellar matter, Molecular clouds, Molecular astrophysics, Astrophysics, Gas dynamics
- Abstract
This book provides an introduction to the physics of interstellar gas in the Galaxy. It deals with the diffuse interstellar medium which supplies a complex environment for exploring the neutral gas content of a galaxy like the Milky Way and the techniques necessary for studying this non-stellar component. After an initial exposition of the phases of the interstellar medium and the role of gas in a spiral galaxy, the authors discuss the transition from atomic to molecular gas. They then consider basic radiative transfer and molecular spectroscopy with particular emphasis on the molecules useful for studying low-density molecular gas. Observational techniques for investigating the gas and the dust component of the diffuse interstellar medium throughout the electromagnetic spectrum are explored emphasizing results from the recent Herschel and Planck missions. A brief exposition on dust in the diffuse interstellar medium is followed by a discussion of molecular clouds in general and high-latitude molecular clouds in particular. Ways of calibrating CO observations with the molecular hydrogen content of a cloud are examined along with the dark molecular gas controversy. High-latitude molecular clouds are considered in detail as vehicles for applying the techniques developed in the book. Given the transient nature of diffuse and translucent molecular clouds, the role of turbulence in the origin and dynamics of these objects is examined in some detail. The book is targeted at graduate students or postdocs who are entering the field of interstellar medium studies.
- Published
- 2017
8. Conductance switching in single light-sensitive molecular device with carbon nanotube electrodes.
- Author
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Cai-Juan Xia, Kun Gao, De-Hua Zhang, Mao Yang, and Fei-Long Feng
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ELECTRIC admittance , *ELECTRODES , *CARBON nanotubes , *MOLECULAR astrophysics , *NONEQUILIBRIUM flow - Abstract
By applying nonequilibrium Green's function formalism combined first-principles density functional theory, a new mechanism for optical switch of single molecular device with carbon nanotube electrodes is proposed. The molecule comprises the switch can convert between enol and keto isomers upon photoinduced excited state hydrogen transfer in the molecular bridge. Theoretical results show that these two isomers exhibit very different current-voltage characteristics both in armchair and zigzag junction, which can realize the on and off states of the molecular switch. Meantime, the chirality of the single-walled carbon nanotube (SWCNT) electrodes strongly affects the switching characteristics of the molecular junctions. The maximum value of on-off ratio can reach 72 at 1.6V for the switch with zigzag SWCNT electrodes, suggesting potential applications of this junction in future design of light-driven molecular switches. [ABSTRACT FROM AUTHOR]
- Published
- 2014
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9. Rotranslational state-to-state rates and spectral representation of inelastic collisions in low-temperature molecular hydrogen.
- Author
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Montero, S., Thibault, F., Tejeda, G., and Fernández, J. M.
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COLLISIONS (Nuclear physics) , *ULTRASONICS , *RELAXATION phenomena , *RAMAN spectroscopy , *ENERGY transfer , *SPECTRUM analysis , *HYPOTHESIS , *MOLECULAR astrophysics - Abstract
Inelastic collisions in natural H2 are studied from the experimental and theoretical points of view between 10 and 140 K. Rotational populations and number densities measured by Raman spectroscopy along supersonic expansions of H2 provide the link between experimental and theoretical rotranslational state-to-state rate coefficients of H2 in the vibrational ground state. These rates are calculated in the close- scattering approach with the MOLSCAT code employing a recent ab initio H2–H2 potential. The calculated rates are assessed by means of a master equation describing the time evolution of the experimental rotational populations. The feasibility for obtaining the rates on the sole basis of the experiment is discussed. The dominant processes j1j2→j1′j2′ in the investigated thermal range are found to be 21→01>30→12>31→11, proving the importance of double processes such as 30→12. Good agreement is found between theory and experiment, as well as with earlier ultrasonic measurements of relaxation times. A spectral representation is proposed in order to visualize quantitatively the collisional contributions in any nonequilibrium time evolving process. [ABSTRACT FROM AUTHOR]
- Published
- 2006
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10. Outflows in the inner kiloparsec of NGC 1566 as revealed by molecular (ALMA) and ionized gas (Gemini-GMOS/IFU) kinematics.
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Slater, R., Nagar, N. M., Schnorr-Müller, A., Storchi-Bergmann, T., Finlez, C., Lena, D., Ramakrishnan, V., Mundell, C. G., Riffel, R. A., Peterson, B., Robinson, A., and Orellana, G.
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MOLECULAR astrophysics , *IONIZATION (Atomic physics) , *KINEMATICS , *MOLECULAR gas lasers , *ROTATIONAL motion - Abstract
Context. Tracing nuclear inflows and outflows in active galactic nuclei (AGNs), determining the mass of gas involved in them, and their impact on the host galaxy and nuclear black hole requires 3D imaging studies of both the ionized and molecular gas. Aims. We map the distribution and kinematics of molecular and ionized gas in a sample of active galaxies to quantify the nuclear inflows and outflows. Here, we analyze the nuclear kinematics of NGC 1566 via ALMA observations of the CO J:2-1 emission at 24 pc spatial and ∼2.6 km s−1 spectral resolution, and Gemini-GMOS/IFU observations of ionized gas emission lines and stellar absorption lines at similar spatial resolution, and 123 km s−1 of intrinsic spectral resolution. Methods. The morphology and kinematics of stellar, molecular (CO), and ionized ([N II]) emission lines are compared to the expectations from rotation, outflows, and streaming inflows. Results. While both ionized and molecular gas show rotation signatures, there are significant non-circular motions in the innermost 200 pc and along spiral arms in the central kpc (CO). The nucleus shows a double-peaked CO profile (full width at zero intensity of 200 km s−1), and prominent (∼80 km s−1) blue- and redshifted lobes are found along the minor axis in the inner arcseconds. Perturbations by the large-scale bar can qualitatively explain all features in the observed velocity field. We thus favor the presence of a molecular outflow in the disk with true velocities of ∼180 km s−1 in the nucleus and decelerating to 0 by ∼72 pc. The implied molecular outflow rate is 5.6 M⊙ yr−1, with this gas accumulating in the nuclear 2″ arms. The ionized gas kinematics support an interpretation of a similar but more spherical outflow in the inner 100 pc, with no signs of deceleration. There is some evidence of streaming inflows of ∼50 km s−1 along specific spiral arms, and the estimated molecular mass inflow rate, ∼0.1 M⊙ yr−1, is significantly higher than the SMBH accretion rate (ṁ = 4.8 × 10−5M⊙ yr−1). [ABSTRACT FROM AUTHOR]
- Published
- 2019
- Full Text
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11. PAH under XUV excitation: an ultrafast XUV-photochemistry experiment for astrophysics.
- Author
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Hervé, M., Castellanos, P., Karras, G., Despré, V., Marciniak, A., Constant, E., Loriot, V., Kuleff, A.I., Tielens, A. G. G. M., Lépine, F., Cerullo, G., Ogilvie, J., Kärtner, F., Khalil, M., and Li, R.
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POLYCYCLIC aromatic hydrocarbons , *PHOTOCHEMISTRY , *MOLECULAR astrophysics , *INTERSTELLAR medium , *NAPHTHALENE - Abstract
Understanding processes induced by XUV excitation of Polycyclic Aromatic Hydrocarbons (PAHs) is at the heart of molecular astrophysics, which aims at understanding molecular evolution in interstellar media. We used ultrashort XUV pulses to produce highly excited PAHs cations. The photo-induced dynamics is probed using a pump-probe XUV-IR spectroscopy. By studying PAH from small (naphthalene) to large (hexabenzocoronene) PAHs, we show that the dynamic is governed by the large density of states, in which many-body quantum effects are dominant. [ABSTRACT FROM AUTHOR]
- Published
- 2019
- Full Text
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12. CHIPS: CHEMISTRY IN OUTFLOWS OF POST-AGB STARS
- Author
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Luis Velilla-Prieto, Javier Alcolea, Valentín Bujarrabal, Arancha Castro-Carrizo, Hans Olofsson, Wouter Vlemmings, Theo Khouri, and Marcelino Agúndez
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Evolved stars ,post-AGB ,Radio Astronomy ,Molecular Astrophysics ,Circumstellar envelopes ,Stellar evolution - Abstract
Among the different types of evolved stars, some post-AGBs experience fast shocks that disrupt their circumstellar envelopes activating a complex chemistry, resembling that of young stellar objects, which is poorly characterized. The CHIPS project aims to understand the complex chemistry of these objects through observations in the (sub)mmand chemical modeling.
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- 2022
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13. Molecular analysis of thyroglobulin mutations found in patients with goiter and hypothyroidism.
- Author
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Siffo, Sofia, Adrover, Ezequiela, Citterio, Cintia E., Rivolta, Carina M., Targovnik, Héctor M., Miras, Mirta B., Sobrero, Gabriela, Balbi, Viviana A., González, Verónica G., Chiesa, Ana, Papendieck, Patricia, Weill, Jacques, Martinez, Elena Bueno, and Gonzalez-Sarmiento, Rogelio
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MOLECULAR astrophysics , *THYROGLOBULIN , *GLOBULINS , *THYROXINE , *HYPOTHYROIDISM - Abstract
Thyroid dyshormonogenesis due to thyroglobulin (TG) gene mutations have an estimated incidence of approximately 1 in 100,000 newborns. The clinical spectrum ranges from euthyroid to mild or severe hypothyroidism. Up to now, one hundred seventeen deleterious mutations in the TG gene have been identified and characterized. The purpose of the present study was to identify and characterize new mutations in the TG gene. We report eight patients from seven unrelated families with goiter, hypothyroidism and low levels of serum TG. All patients underwent clinical, biochemical and image evaluation. Sequencing of DNA, genotyping, as well as bioinformatics analysis were performed. Molecular analyses revealed three novel inactivating TG mutations: c.5560G>T [p.E1835*], c.7084G>C [p.A2343P] and c.7093T>C [p.W2346R], and four previously reported mutations: c.378C>A [p.Y107*], c.886C>T [p.R277*], c.1351C>T [p.R432*] and c.7007G>A [p.R2317Q]. Two patients carried homozygous mutations (p.R277*/p.R277*, p.W2346R/p.W2346R), four were compound heterozygous mutations (p.Y107*/p.R277* (two unrelated patients), p.R432*/p.A2343P, p.Y107*/p.R2317Q) and two siblings from another family had a single p.E1835* mutated allele. Additionally, we include the analysis of 48 patients from 31 unrelated families with TG mutations identified in our present and previous studies. Our observation shows that mutations in both TG alleles were found in 27 families (9 as homozygote and 18 as heterozygote compound), whereas in the remaining four families only one mutated allele was detected. The majority of the detected mutations occur in exons 4, 7, 38 and 40. 28 different mutations were identified, 33 of the 96 TG alleles encoded the change p.R277*. In conclusion, our results confirm the genetic heterogeneity of TG defects and the pathophysiological importance of the predicted TG misfolding and therefore thyroid hormone formation as a consequence of truncated TG proteins and/or missense mutations located within its ACHE-like domain. [ABSTRACT FROM AUTHOR]
- Published
- 2018
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14. The surface reactivity of acrylonitrile with oxygen atoms on an analogue of interstellar dust grains.
- Author
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Kimber, Helen J., Toscano, Jutta, and Price, Stephen D.
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INTERPLANETARY dust , *SURFACE reactions , *MOLECULAR astrophysics , *INTERSTELLAR molecules , *ACRYLONITRILE , *ASTROCHEMISTRY , *TIME-of-flight mass spectrometry - Abstract
Experiments designed to reveal the low-temperature reactivity on the surfaces of interstellar dust grains are used to probe the heterogeneous reaction between oxygen atoms and acrylonitrile (C2H3CN, H2C=CH-CN). The reaction is studied at a series of fixed surface temperatures between 14 and 100 K. After dosing the reactants on to the surface, temperature-programmed desorption, coupled with time-of-flight mass spectrometry, reveals the formation of a product with themolecular formula C3H3NO. This product results from the addition of a single oxygen atom to the acrylonitrile reactant. The oxygen atom attack appears to occur exclusively at the C=C double bond, rather than involving the cyano(-CN) group. The absence of reactivity at the cyano site hints that full saturation of organic molecules on dust grains may not always occur in the interstellar medium. Modelling the experimental data provides a reaction probability of 0.007 ± 0.003 for a Langmuir--Hinshelwood style (diffusive) reaction mechanism. Desorption energies for acrylonitrile, oxygen atoms, and molecular oxygen, from the multilayer mixed ice their deposition forms, are also extracted from the kinetic model and are 22.7 ± 1.0 kJ mol-1 (2730 ± 120 K), 14.2 ± 1.0 kJ mol-1 (1710 ± 120 K), and 8.5 ± 0.8 kJ mol-1 (1020 ± 100 K), respectively. The kinetic parameters we extract from our experiments indicate that the reaction between atomic oxygen and acrylonitrile could occur on interstellar dust grains on an astrophysical time-scale. [ABSTRACT FROM AUTHOR]
- Published
- 2018
- Full Text
- View/download PDF
15. ALMA view of RX J1131-1231: Sub-kpc CO (2-1) mapping of a molecular disk in a lensed star-forming quasar host galaxy.
- Author
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Paraficz, D., Rybak, M., McKean, J. P., Vegetti, S., Sluse, D., Courbin, F., Stacey, H. R., Suyu, S. H., Dessauges-Zavadsky, M., Fassnacht, C. D., and Koopmans, L. V. E.
- Subjects
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STAR formation , *QUASARS , *SPECTRAL lines , *MOLECULAR astrophysics - Abstract
We present ALMA 2-mm continuum and CO (2-1) spectral line imaging of the gravitationally lensed z = 0.654 star-forming/quasar composite RX J1131-1231 at 240-400 mas angular resolution. The continuum emission is found to be compact and coincident with the optical emission, whereas the molecular gas forms a complete Einstein ring, which shows strong differential magnification. The de-lensed source structure is determined on 400-parsec-scales resolution using a Bayesian pixelated visibility-fitting lens modelling technique. The reconstructed molecular gas velocity-field is consistent with a large rotating disk with a major-axis FWHM ~9.4 kpc at an inclination angle of i = 54° and with a maximum rotational velocity of 280 km s-1. From dynamical model fitting we find an enclosed mass within 5 kpc of M(r < 5 kpc) = (1.46±0.31) × 1011 M☉. The molecular gas distribution is highly structured, with clumps that are co-incident with higher gas velocity dispersion regions (40-50 km s-1) and with the intensity peaks in the optical emission, which are associated with sites of on-going turbulent star-formation. The peak in the CO (2-1) distribution is not co-incident with the AGN, where there is a paucity of molecular gas emission, possibly due to radiative feedback from the central engine. The intrinsic molecular gas luminosity is L0 CO = 1.2±0.3 × 1010 K km s-1 pc2 and the inferred gas mass is MH2 = 8.3±3.0 × 1010 M☉, which given the dynamical mass of the system is consistent with a CO-H2 conversion factor of α = 5.5±2.0 M☉ (K km s-1 pc2)-1. This suggests that the star-formation efficiency is dependent on the host galaxy morphology as opposed to the nature of the AGN. The far-infrared continuum spectral energy distribution shows evidence for heated dust, equivalent to an obscured star-formation rate of SFR = 69+41-25 × (7.3=μIR) M☉ yr-1, which demonstrates the composite star-forming and AGN nature of this system. [ABSTRACT FROM AUTHOR]
- Published
- 2018
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16. Diagnosis of a short-pulse dielectric barrier discharge at atmospheric pressure in helium with hydrogen-methane admixtures.
- Author
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Nastuta, A. V., Pohoata, V., Mihaila, I., and Topala, I.
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DIELECTRICS , *ATMOSPHERIC pressure , *GAS mixtures , *CURRENT density (Electromagnetism) , *MOLECULAR astrophysics - Abstract
In this study, we present results from electrical, optical, and spectroscopic diagnosis of a short-pulse (250 ns) high-power impulse (up to 11 kW) dielectric barrier discharge at atmospheric pressure running in a helium/helium-hydrogen/helium-hydrogen-methane gas mixture. This plasma source is able to generate up to 20 cm3 of plasma volume, pulsed in kilohertz range. The plasma spatio-temporal dynamics are found to be developed in three distinct phases. All the experimental observations reveal a similar dynamic to medium power microsecond barrier discharges, although the power per pulse and current density are up to two orders of magnitude higher than the case of microsecond barrier discharges. This might open the possibility for new applications in the field of gas or surface processing, and even life science. These devices can be used in laboratory experiments relevant for molecular astrophysics. [ABSTRACT FROM AUTHOR]
- Published
- 2018
- Full Text
- View/download PDF
17. The evolution of the protoplanetary disk with mass influx from a molecular cloud core and the photoevaporation winds.
- Author
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Liu, Chunjian, Yao, Zhen, Li, Hongna, and Wang, Haosen
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PROTOPLANETARY disks , *ACCRETION (Astrophysics) , *CLOUD dynamics , *MOLECULAR astrophysics , *MAGNETOHYDRODYNAMICS , *MATHEMATICAL models - Abstract
We investigate the formation, evolution, and dispersal processes of protoplanetary disks with mass influx from the gravitational collapse of a molecular cloud core and the photoevaporation winds. Due to the initial angular momentum of the molecular cloud core, the gravitational collapse of the molecular cloud core forms a protostar+protoplanetary disk system. We calculate the evolution of the protoplanetary disk from the gravitational collapse of the molecular cloud core to the dispersal stage. In our calculation, we include the mass influx from a molecular cloud core, the irradiation from the central star, the viscosity due to the magnetohydrodynamic (MHD) turbulence driven by the magnetorotational instability (MRI) and the gravitational instability, and the effect of photoevaporation. We find that the protoplanetary disk has some interesting properties, which are different from the previous studies. Firstly, with particular values of parameters of the molecular cloud core, the gravitational instability does not occur during the whole evolution of the resultant protoplanetary disk. With some other parameters of the molecular cloud core, the gravitational instability occurs all the time of the lifetime of the resultant protoplanetary disk. Secondly, the radial distribution of the α parameter exhibits a nearly ladder-like shape, which is different from the three regions’ shape in previous studies. Thirdly, the value of the surface density is increased significantly (about a factor of 8.0) compared with that in the Minimum Mass Solar Nebula (MMSN) model. We suggest that this increased surface density can provide enough material for the formation of giant planets within the lifetime of the protoplanetary disk, and may provide a routine for reducing the timescale of the formation of giant planets. We also discuss the influence of the photoevaporation winds on the evolution of the protoplanetary disk. [ABSTRACT FROM AUTHOR]
- Published
- 2018
- Full Text
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18. Chemical Evolution of Protostars
- Author
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Hogerheijde, Michiel R., Baan, W.A., editor, Hagiwara, Y., editor, and van Langevelde, H.J., editor
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- 2005
- Full Text
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19. Molecular Physics in Storage Rings: From Laboratory to Space
- Author
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Zajfman, D., Schwalm, D., Wolf, A., Knudsen, Helge, editor, Andersen, Jens Ulrik, editor, and Kluge, Heinz-Jürgen, editor
- Published
- 2003
- Full Text
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20. Effects of disc mid-plane evolution on CO snowline location.
- Author
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Panić, O. and Min, M.
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ORIGIN of planets , *PROTOPLANETARY disks , *MOLECULAR astrophysics , *PLANETARY temperature , *INTERPLANETARY dust - Abstract
Temperature changes in the planet forming disc mid-planes carry important physico-chemical consequences, such as the effect on the locations of the condensation fronts of molecules - the snowlines. Snowlines impose major chemical gradients and possibly foster grain growth. The aim of this paper is to understand how disc mid-plane temperature changes with gas and dust evolution, and identify trends that may influence planet formation or allow to constrain disc evolution observationally. We calculate disc temperature, hydrostatic equilibrium and dust settling in a mutually consistent way from a grid of disc models at different stages of gas loss, grain growth and hole opening. We find that the CO snowline location depends very strongly on disc properties. The CO snowline location migrates closer to the star for increasing degrees of gas dispersal and dust growth. Around a typical A-type star, the snowline can be anywhere between several tens and a few hundred au, depending on the disc properties such as gas mass and grain size. In fact, gas loss is as efficient as dust evolution in settling discs, and flat discs may be gas-poor counterparts of flared discs. Our results, in the context of different pre-main-sequence evolution of the luminosity in low- and intermediate-mass stars suggest very different thermal (and hence chemical) histories in these two types of discs. Discs of T Tauri stars settle and cool down, while discs of Herbig Ae stars may remain rather warm throughout the pre-main sequence. [ABSTRACT FROM AUTHOR]
- Published
- 2017
- Full Text
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21. Dust scattering from the Taurus Molecular Cloud.
- Author
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Narayan, Sathya, Murthy, Jayant, and Karuppath, Narayanankutty
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MOLECULAR clouds , *INTERSTELLAR molecules , *HIGH-velocity clouds (Astrophysics) , *COSMOCHEMISTRY , *MOLECULAR astrophysics - Abstract
We present an analysis of the diffuse ultraviolet emission near the Taurus Molecular Cloud based on observations made by the Galaxy Evolution Explorer. We used a Monte Carlo dust scattering model to show that about half of the scattered flux originates in the molecular cloud with 25 per cent arising in the foreground and 25 per cent behind the cloud. The best-fitting albedo of the dust grains is 0.3, but the geometry is such that we could not constrain the phase function asymmetry factor (g). [ABSTRACT FROM AUTHOR]
- Published
- 2017
- Full Text
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22. HC3N observations of nearby galaxies.
- Author
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Xue-Jian Jiang, Jun-Zhi Wang, Yu Gao, and Qiu-Sheng Gu
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GALAXIES , *MOLECULAR astrophysics , *GAS dynamics , *ASTRONOMICAL observations , *ASTRONOMICAL measurements - Abstract
Aims. We aim to systematically study the properties of the different transitions of the dense molecular gas tracer HC3N in galaxies. Methods. We have conducted single-dish observations of HC3N emission lines towards a sample of nearby gas-rich galaxies. HC3N(J = 2-1) was observed in 20 galaxies with the Effelsberg 100-m telescope. HC3N(J = 24-23) was observed in nine galaxies with the 10-m Submillimeter Telescope (SMT). Results. HC3N 2-1 is detected in three galaxies: IC 342, M 66, and NGC 660 (>3σ). HC3N 24-23 is detected in three galaxies: IC 342, NGC 1068, and IC 694. These are the first measurements of HC3N 2-1 in a relatively large sample of external galaxies, although the detection rate is low. For the HC3N 2-1 non-detections, upper limits (2σ) are derived for each galaxy, and stacking the non-detections is attempted to recover the weak signal of HC3N. The stacked spectrum, however, does not show any significant signs of HC3N 2-1 emission. The results are also compared with other transitions of HC3N observed in galaxies. Conclusions. The low detection rate of both transitions suggests low abundance of HC3N in galaxies, which is consistent with other observational studies. The comparison between HC3N and HCN or HCO+ shows a large diversity in the ratios between HC3N and HCN or HCO+. More observations are needed to interpret the behavior of HC3N in different types of galaxies. [ABSTRACT FROM AUTHOR]
- Published
- 2017
- Full Text
- View/download PDF
23. An efficient and high fidelity method for amplification, cloning and sequencing of complete tospovirus genomic RNA segments.
- Author
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Marshall, Spencer H., Adegbola, Raphael O., Adkins, Scott, and Naidu, Rayapati A.
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- *
AMPLIFICATION reactions , *GENOMIC imprinting , *NON-coding RNA , *MOLECULAR astrophysics , *NUCLEOCAPSIDS - Abstract
Tospoviruses (genus Tospovirus , family Bunyaviridae ) are responsible for major losses in an extensive range of crops worldwide. New species of these single-stranded, ambisense RNA viruses regularly emerge and have been shown to maintain heterogeneous populations with individual isolates having quite variable biological and virulence characteristics. Most tospovirus phylogenetic studies have focused on analysis of a single gene, most often the nucleocapsid protein gene. Complete genomic RNA segment amplification as a single fragment would facilitate more detailed analyses of genome-wide sequence variability, but obtaining such sequences for a large number of tospovirus isolates using traditional methods of amplification and cloning of small overlapping fragments is tedious, time consuming and expensive. In this study, protocols were optimized to amplify, clone and sequence full-length M- and S-RNA genome segments of Tomato spotted wilt virus and Impatiens necrotic spot virus . The strategy presented here is straightforward, scalable and offers several advantages over the previously commonplace and overlapping amplicon-based approach. Use of whole genome segments, instead of individual gene sequences or defined portions of genome segments, will facilitate a better understanding of the underlying molecular diversity of tospoviruses in mixed infections. [ABSTRACT FROM AUTHOR]
- Published
- 2017
- Full Text
- View/download PDF
24. Molecular outflows in starburst nuclei.
- Author
-
Roy, Arpita, Nath, Biman B., Sharma, Prateek, and Shchekinov, Yuri
- Subjects
- *
MOLECULAR astrophysics , *GALACTIC nuclei , *SUPERGIANT stars , *MOLECULES , *ACTINIC flux - Abstract
Recent observations have detected molecular outflows in a few nearby starburst nuclei. We discuss the physical processes at work in such an environment in order to outline a scenario that can explain the observed parameters of the phenomenon, such as the molecular mass, speed and size of the outflows. We show that outflows triggered by OB associations, with NOB ≥ 105 (corresponding to a star formation rate (SFR)≥1 M☉ yr-1 in the nuclear region), in a stratified disc with mid-plane density n0 ~ 200-1000 cm-3 and scaleheight z0 ≥ 200(n0/102 cm-3)-3/5 pc, can form molecules in a cool dense and expanding shell. The associated molecular mass is ≥107M☉ at a distance of a few hundred pc, with a speed of several tens of km s-1. We show that an SFR surface density of 10 ≤ ΣSFR ≤ 50 M☉ yr-1 kpc-2 favours the production of molecular outflows, consistent with observed values. [ABSTRACT FROM AUTHOR]
- Published
- 2016
- Full Text
- View/download PDF
25. Molecular Collisions in the Interstellar Medium
- Author
-
David Flower and David Flower
- Subjects
- Molecular astrophysics, Molecular dynamics, Interstellar matter
- Abstract
In the interstellar medium - the space between the stars in galaxies - new stars are born from material that is replenished by the debris ejected by stars when they die. This book is a comprehensive manual for studying the collisional and radiative processes observed in the interstellar medium. This second edition has been thoroughly updated and extended to cover related topics in radiation theory. It considers the chemistry of the interstellar medium both at the present epoch and in the early Universe, and discusses the physics and chemistry of shock waves. The methods of calculation of the rates of collisional excitation of interstellar molecules and atoms are explained, emphasising the quantum mechanical method. This book will be ideal for researchers involved in the interstellar medium and star formation, and physical chemists specialising in collision theory or in the measurement of the rates of collision processes.
- Published
- 2007
26. The Chemistry of Molecular Anions in Circumstellar Sources.
- Author
-
Agúndez, Marcelino, Cernicharo, José, and Guélin, Michel
- Subjects
- *
ANIONS , *CIRCUMSTELLAR matter , *INTERSTELLAR medium , *MOLECULAR astrophysics , *N stars , *MOLECULAR clouds - Abstract
The detection of negatively charged molecules in the interstellar and circumstellar medium in the past four years has been one of the most impacting surprises in the area of molecular astrophysics. It has motivated the interest of astronomers, physicists, and chemists on the study of the spectroscopy, chemical kinetics, and prevalence of molecular anions in the different astronomical regions. Up to six different molecular anions have been discovered in space to date, the last one being the small ion CN-, which has been observed in the envelope of the carbon star IRC +10216 and which contrary to the other larger anions is not formed by electron attachment to CN, but through reactions of large carbon anions with nitrogen atoms. Here we briefly review the current status of our knowledge of the chemistry of molecular anions in space, with particular emphasis on the circumstellar source IRC +10216, which to date is the astronomical source harboring the largest variety of anions. [ABSTRACT FROM AUTHOR]
- Published
- 2015
- Full Text
- View/download PDF
27. Time-resolved fourier transform infrared emission spectroscopy of NH radical in the X3Σ− ground state.
- Author
-
Pastorek, Adam, Clark, Victoria H.J., Yurchenko, Sergei N., and Civiš, Svatopluk
- Subjects
- *
FOURIER transform infrared spectroscopy , *MICROWAVE spectroscopy , *GLOW discharges , *FOURIER transform spectroscopy , *ELECTRIC discharges - Abstract
• T-R FTIR spectroscopy of NH radical. • Generation of species in glow discharge of N 2 +H 2 and N 2 +NH 3 +Ar mixtures. • Analysis of decomposition products together with time profiles. • Pure rotation transitions first observed in the lab by use of cold source. • Non-LTE modelling of obtained spectra. The NH radical is an extremely important specie in nitrogen chemical reaction networks, in the interstellar medium and atmospheric chemistry. Time resolved Fourier transform spectroscopy technique in the frequency range 10–13 µm has been applied for the measurement of a pure rotational spectrum of the NH free radical (NH) in the ground X3Σ− electronic state. Twelve high N (26–29) triplet-resolved pure rotation lines of NH were experimentally observed in the laboratory and compared with satellite ACE (Atmospheric Chemistry Experiment) solar data. In addition, discharge-generated vibration-rotation NH radical bands in the spectral range 1923–3571 cm−1 have been measured with a microsecond time resolution and spectral resolution of 0.02 cm−1. The spectra of the NH radical have been studied in two experimental arrangements. Firstly, in a pulsed positive column discharge of pure hydrogen-nitrogen mixture and secondly, in a discharge of nitrogen-ammonia mixture in the presence of argon buffer gas. Both production methods are described and compared. The population analysis of the experimental spectra was performed via modelling using the accurate MoLLIST line lists for NH. It was shown that laboratory data can be well reproduced by use of a mixture of the local-thermal-equilibrium (LTE) and non-LTE models corresponding to high temperatures (up to 8000 K and up to 6000 K rotational). [ABSTRACT FROM AUTHOR]
- Published
- 2022
- Full Text
- View/download PDF
28. USING CO TO MEASURE MOLECULAR MASSES.
- Author
-
Bolatto, A. D.
- Subjects
- *
GALACTIC evolution , *MOLECULAR astrophysics , *STELLAR mass , *CARBON monoxide , *ASTRONOMICAL research - Abstract
With an increased appreciation for the role of gas in galaxy evolution, there is renewed interest in measuring gas masses for galaxies. I review some of the basic concepts in using CO to determine molecular masses, and discuss some of the recent work. [ABSTRACT FROM AUTHOR]
- Published
- 2015
- Full Text
- View/download PDF
29. ASTROCHEMISTRY AND STAR FORMATION IN NEARBY GALAXIES: FROM GALAXY DISKS TO HOT NUCLEI.
- Author
-
Aalto, S.
- Subjects
- *
STAR formation , *ASTROCHEMISTRY , *DISKS (Astrophysics) , *GALACTIC nuclei , *MOLECULAR astrophysics , *INTERSTELLAR medium - Abstract
Studying the molecular phase of the interstellar medium in galaxies is fundamental for the understanding of the onset and evolution of compact and extended star formation, and of the growth of supermassive black holes. Molecular line emission is an excellent tracer of chemical, physical and dynamical conditions in the cold neutral gas. Key molecules in extragalactic studies are e.g. HCN, HCO+, HC3N, SiO, CH3OH, H2O. Furthermore, we can use IR excited molecular emission to probe the very inner regions of luminous infrared galaxies allowing us to get past the optically thick dust barrier of the compact obscured nuclei where lines of CO, HCN and HCO+ in their vibrational ground state (v=0) may be self-absorbed. Finally, molecular outflows and their chemistry are briefly discussed - including new ALMA results on for example the outflow of the lenticular galaxy NGC1377 and a study of the chemistry of the outflow of the quasar Mrk231. [ABSTRACT FROM AUTHOR]
- Published
- 2015
- Full Text
- View/download PDF
30. The reactivity of methanimine radical cation (H2CNH.+) and its isomer aminomethylene (HCNH2.+) with methane
- Author
-
Richardson, V., Alcaraz, C., Geppert, Wolf, Polášek, M., Romanzin, C., Sundelin, David, Thissen, R., Tosi, P., Žabka, J., Ascenzi, D., Richardson, V., Alcaraz, C., Geppert, Wolf, Polášek, M., Romanzin, C., Sundelin, David, Thissen, R., Tosi, P., Žabka, J., and Ascenzi, D.
- Abstract
Experimental and theoretical studies are presented on the reactions of the isomeric radical cations H2CNH+ and HCNH2+ with CH4. Ionic isomers were generated selectively by VUV dissociative photoionization of azetidine and cyclopropylamine precursors respectively. Both exclusively give H2CNH2+ plus CH3 as products, but differences are observed related to a competition between stripping and complex-mediated H-transfer. Astrochemical implications for Titan’s atmosphere are briefly discussed, where the presence of methanimine (H2CNH), a key prebiotic molecule and a potential precursor for tholins, is proposed on the basis of atmospheric models and the observation of CH2NH2+ ions in Cassini mass spectrometric data.
- Published
- 2021
- Full Text
- View/download PDF
31. The Physics and Chemistry of the Interstellar Medium
- Author
-
A. G. G. M. Tielens and A. G. G. M. Tielens
- Subjects
- Interstellar matter, Molecular astrophysics, Galaxies
- Abstract
This work provides a comprehensive overview of our theoretical and observational understanding of the interstellar medium of galaxies. With emphasis on the microscopic physical and chemical processes in space, and their influence on the macroscopic structure of the interstellar medium of galaxies, the book includes developments in this area of molecular astrophysics. The various heating, cooling, and chemical processes relevant for the rarefied gas and submicron-sized dust grains that constitute the interstellar medium are discussed in detail. This provides a firm foundation for an in-depth understanding of the ionized, neutral atomic, and molecular phases of the interstellar medium. The physical and chemical properties of large polycyclic aromatic hydrocarbon molecules and their role in the interstellar medium are highlighted, and the physics and chemistry of warm and dense photodissociation regions are discussed. This is an invaluable reference source for advanced undergraduate and graduate students, and research scientists.
- Published
- 2005
32. First experimental photo-detachment spectrum of H2−.
- Author
-
Rudnev, Vitaly, Schlösser, Magnus, Telle, Helmut H., and González Ureña, Ángel
- Subjects
- *
PHOTODETACHMENT , *HYDROGEN ions , *EXCITATION energy (In situ microanalysis) , *MOLECULAR astrophysics , *ELECTRODYNAMICS , *PLASMA physics - Abstract
This letter reports the first photo-detachment spectrum of the hydrogen anion, H 2 − . The spectrum was recorded over the range of excitation energies E hν = 17 600–17 750 cm −1 , at known laser fluence and under non-saturation conditions. This permitted us to extract absolute values for the photo-depletion cross-section which varies in the range 1–6 × 10 −18 cm 2 and exhibits oscillatory behaviour. This interesting behaviour was attributed to an electro-dynamical interaction between of the highly-rotating hydrogen daughter molecule and the detached electron. The presence of such oscillations may open new ways to investigate exotic anions relevant to molecular astrophysics and plasma physics. [ABSTRACT FROM AUTHOR]
- Published
- 2015
- Full Text
- View/download PDF
33. Rotational spectral studies of O(1D) insertion reactions with methane and ethylene: Methanol and vinyl alcohol in a supersonic expansion.
- Author
-
Hays, Brian M., Wehres, Nadine, DePrince, Bridget Alligood, Roy, Althea A.M., Laas, Jacob C., and Widicus Weaver, Susanna L.
- Subjects
- *
INSERTION reactions (Chemistry) , *METHANE , *ETHYLENE , *METHANOL , *ULTRASONICS , *MOLECULAR astrophysics - Abstract
We report a new apparatus for millimeter/submillimeter spectroscopic studies of O( 1 D) insertion reactions to produce molecules of astrophysical interest. This study focuses on the insertion of O( 1 D) into methane to form methanol, and the insertion of O( 1 D) into ethylene to form vinyl alcohol (CH 2 CHOH). The O( 1 D) was produced via laser photodissociation of O 3 in a fused silica tube and mixed with a hydrocarbon before a supersonic expansion. Direct absorption millimeter/submillimeter spectroscopy was used to monitor the products. The methanol study was used as an experimental benchmark, while the vinyl alcohol study extended rotational spectroscopic measurements to higher frequencies. Observed products from both insertion reactions included, but were not limited to, H 2 CO, HO 2 , and CH 3 O. Methanol and vinyl alcohol were only produced in detectable quantities when the fused silica tube was included, indicating that collisions before the expansion are required for production and stabilization of the O( 1 D) insertion products. [ABSTRACT FROM AUTHOR]
- Published
- 2015
- Full Text
- View/download PDF
34. EXPERIMENTAL AND COMPUTATIONAL STUDIES OF THE FORMATION MECHANISM OF PROTONATED INTERSTELLAR DIAZINES.
- Author
-
ZHE-CHEN WANG, COLE, CALLIE A., SNOW, THEODORE P., and BIERBAUM, VERONICA M.
- Subjects
- *
DIAZINES , *INTERSTELLAR molecules , *INTERSTELLAR medium , *MOLECULAR astrophysics , *AZINES , *COLLISION induced dissociation - Abstract
Studies of interstellar chemistry have grown in number and complexity by both observations and laboratory measurements, and nitrogen-containing aromatics have been implicated as important interstellar molecules. In this paper, the gas-phase collision induced dissociation (CID) processes of protonated pyridazine (1,2-diazine), pyrimidine (1,3-diazine), and pyrazine (1,4-diazine) cations (C4H5N2 + ) are investigated in detail both experimentally and theoretically. The major neutral loss for all three CID processes is HCN, leading to the formation of C3H4N+ isomers; our density functional theory (DFT) calculations support and elucidate our experimental results. The formation of C3H4N+ isomers from the reaction of abundant interstellar acrylonitrile (CH2CHCN) and H+ is also studied employing DFT calculations. Our results lead to a novel mechanism for interstellar protonated diazine formation from the consecutive reactions of CH2CHCN + H+ + HCN. Moreover, our results motivate the continuing search for interstellar C3H4N+ isomers as well as polycyclic aromatic N-containing hydrocarbons (PANHs). [ABSTRACT FROM AUTHOR]
- Published
- 2015
- Full Text
- View/download PDF
35. Fast molecular jet from L1157-mm.
- Author
-
Tafalla, M., Bachiller, R., Lefloch, B., Rodríguez-Fernández, N., Codella, C., López-Sepulcre, A., and Podio, L.
- Subjects
- *
PROTOSTARS , *LOW mass stars , *JETS (Fluid dynamics) , *HOT spots (Astronomy) , *MOLECULAR astrophysics , *SILICON oxide spectra - Abstract
Context. L1157-mm powers a molecular outflow that is well-known for its shock-induced chemical activity in several hot-spots. Aims. We have studied the molecular emission toward L1157-mm searching for a jet component responsible for these spots. Methods. We used the IRAM 30 m telescope to observe the vicinity of L1157-mm in several lines of SiO. Results. The SiO(5-4) and SiO(6-5) spectra toward L1157-mm present blue and red detached components about 45 km s-1 away from the ambient cloud. These extremely high-velocity (EHV) components are similar to those found in the L1448 and IRAS 04166+2706 outflows and probably arise from a molecular jet driven by L1157-mm. Observations of off-center positions indicate that the jet is unresolved in SiO(5-4) (<11"). Conclusions. The EHV jet seen in SiO probably excites L1157-B1 and the other chemically active spots of the L1157 outflow. [ABSTRACT FROM AUTHOR]
- Published
- 2015
- Full Text
- View/download PDF
36. Far-infrared excess emission as a tracer of disk-halo interaction.
- Author
-
Lenz, D., Kerp, J., Flöer, L., Winkel, B., Boulanger, F., and Lagache, G.
- Subjects
- *
FAR infrared lasers , *DISKS (Astrophysics) , *STELLAR evolution , *MILKY Way , *HIGH-velocity clouds (Astrophysics) , *MOLECULAR astrophysics - Abstract
Context. Given the current and past star-formation in the Milky Way in combination with the limited gas supply, the re-fuelling of the reservoir of cool gas is an important aspect of Galactic astrophysics. The infall of Hi halo clouds can, among other mechanisms, contribute to solving this problem. Aims. We study the intermediate-velocity cloud IVC135+54 and its spatially associated high-velocity counterpart to look for signs of a past or ongoing interaction. Methods. Using the Effelsberg-Bonn Hi Survey data, we investigated the interplay of gas at different velocities. In combination with far-infrared Planck and IRIS data, we extended this study to interstellar dust and used the correlation of the data sets to infer information on the dark gas. Results. The velocity structure indicates a strong compression and deceleration of the infalling high-velocity cloud (HVC), associated with far-infrared excess emission in the intermediate-velocity cloud. This excess emission traces molecular hydrogen, confirming that IVC135+54 is one of the very few molecular halo clouds. The high dust emissivity of IVC135+54 with respect to the local gas implies that it consists of disk material and does not, unlike the HVC, have an extragalactic origin. Conclusions. Based on the velocity structure of the HVC and the dust content of the IVC, a physical connection between them appears to be the logical conclusion. Since this is not compatible with the distance difference between the two objects, we conclude that this particular HVC might be much closer to us than complex C. Alternatively, the indicators for an interaction are misleading and have another origin. [ABSTRACT FROM AUTHOR]
- Published
- 2015
- Full Text
- View/download PDF
37. New insights on the recoiling/binary black hole candidate J0927+2943 via molecular gas observations.
- Author
-
Decarli, R., Dotti, M., Mazzucchelli, C., Montuori, C., and Volonteri, M.
- Subjects
- *
BINARY systems (Astronomy) , *BINARY black holes , *ASTRONOMICAL observations , *INTERFEROMETERS , *MOLECULAR astrophysics - Abstract
The peculiar QSO J0927+2943 shows multiple sets of emission lines in its optical spectrum. This signature has been interpreted as the relative motion between a black hole, either recoiling or bound in a binary system, and its host galaxy, or as a superposition of two galaxies along the line of sight. In order to test these scenarios, we have collected 2 mm CO(2-1) observations using the IRAM Plateau de Bure Interferometer, and optical images and spectroscopy at the Calar Alto observatory. Together with archival HST images, these data provide unique insights on the nature of this system. The recoiling/binary black hole scenarios are ruled out by the clear detection of a galactic-scale molecular gas reservoir at the same redshift of the QSO broad lines. The observations presented here also disfavour the superposition model, although with less constraints. Thus, the origin of the second, bright set of narrow emission lines in J0927+2943 is still unknown. [ABSTRACT FROM AUTHOR]
- Published
- 2014
- Full Text
- View/download PDF
38. Molecules with a peptide link in protostellar shocks: a comprehensive study of L1157.
- Author
-
Mendoza, Edgar, Lefloch, B., López-Sepulcre, A., Ceccarelli, C., Codella, C., Boechat-Roberty, H. M., and Bachiller, R.
- Subjects
- *
INTERSTELLAR molecules , *MOLECULAR astrophysics , *FORMAMIDE , *ACETAMIDE , *ASTROCHEMISTRY , *ISOCYANIC acid , *STATISTICAL correlation - Abstract
Interstellar molecules with a peptide link (–NH–C(=O)–), like formamide (NH2CHO), acetamide (NH2COCH3) and isocyanic acid (HNCO), are particularly interesting for their potential role in pre-biotic chemistry. We have studied their emission in the protostellar shock regions L1157-B1 and L1157-B2, with the IRAM 30 m telescope, as part of the ASAI Large Programme. Analysis of the line profiles shows that the emission arises from the outflow cavities associated with B1 and B2. Molecular abundances of ≈(0.4–1.1) × 10−8 and (3.3–8.8) × 10−8 are derived for formamide and isocyanic acid, respectively, from a simple rotational diagram analysis. Conversely, NH2COCH3 was not detected down to a relative abundance of a few ≤10−10. B1 and B2 appear to be among the richest Galactic sources of HNCO and NH2CHO molecules. A tight linear correlation between their abundances is observed, suggesting that the two species are chemically related. Comparison with astrochemical models favours molecule formation on icy grain mantles, with NH2CHO generated from hydrogenation of HNCO. [ABSTRACT FROM PUBLISHER]
- Published
- 2014
- Full Text
- View/download PDF
39. Outflows and disks of brown dwarfs with SMA, CARMA and ALMA.
- Author
-
Phan-Bao, Ngoc, Lee, Chin-Fei, Ho, Paul, Martín, Eduardo, and Tho, Do D.
- Subjects
- *
BROWN dwarf stars , *TEMPERATURE of stars , *SUBMILLIMETER astronomy , *MILLIMETER astronomy , *DWARF planets , *MOLECULAR astrophysics - Abstract
Brown dwarfs are on the dividing line between planets and stars. Up to date, about 1,000 brown dwarfs, including the coolest known brown dwarfs with temperatures of ~300K as cool as the human body, have been discovered. However, the origin of these objects is still not well understood. Here we report our study of molecular outflows and disks of young very-low mass stars and brown dwarfs in ρ Ophiuchi and Taurus using the Submillimeter Array (SMA) and the Combined Array for Research in Millimeterwave Astronomy (CARMA). The observations of brown dwarfs at early stages provide key information to understand their formation mechanism as well as planet formation around these very low-mass objects. We also discuss future observations of brown dwarfs with the Atacama Large Millimeter/submillimeter Array (ALMA). [ABSTRACT FROM AUTHOR]
- Published
- 2013
- Full Text
- View/download PDF
40. Modelling of the Earth's transmission spectrum in the framework of one-slab model.
- Author
-
Polinovskyi, G., Pavlenko, Ya V., and Martin, E. L.
- Subjects
- *
MOLECULAR astrophysics , *SPECTRUM analysis , *ASTRONOMICAL models , *LUNAR eclipses , *EXTRASOLAR planets , *PLANETARY observations - Abstract
We discuss the possibility of using the transmission spectrum of the Earth in the measurements of the molecules abundance ratios. We use optical and near infrared transmission spectrum of the Earth obtained during observations of a lunar eclipse in 2008 by Enric Palle and others (E. Pallé et al., 2009). This task is interesting in terms of estimation of the chemical composition of the Earth-like planets around other stars during their transits. We use one-slab model approach for modelling transmission spectra using HITRAN line database. Comparison with observational data gives us clues to our problem. [ABSTRACT FROM AUTHOR]
- Published
- 2013
- Full Text
- View/download PDF
41. Laboratory Simulations of Molecular Hydrogen Formation in the Early Universe: A Progress Report.
- Author
-
Savin, D. W., Bruhns, H., Glover, S. C. O., Kreckel, H., Miller, K., and Urbain, X.
- Subjects
- *
MOLECULAR astrophysics , *SIMULATION methods & models , *HYDROGEN , *INFLATIONARY universe , *STAR formation , *UNCERTAINTY (Information theory) , *PHYSICS laboratories , *STELLAR mass - Abstract
During the epoch of protogalaxy and first star formation, H2 is the main coolant of primordial gas for temperatures below ∼8,000 K. The H2 is formed via associative detachment (AD) of H- and H. Uncertainties in the rate coefficient for this reaction have limited our understanding of protogalaxy formation during this epoch and of the characteristic masses and cooling times for the first stars. Recently we have carried out a series of laboratory measurements which remove these uncertainties. Here, we present the cosmological motivation for our work, describe the experimental approach, and point the reader to the relevant works where our AD results are reported and their cosmological implications explored. [ABSTRACT FROM AUTHOR]
- Published
- 2010
- Full Text
- View/download PDF
42. Formation of Primordial Stars.
- Author
-
Yoshida, Naoki
- Subjects
- *
SUPERGIANT stars , *COSMOLOGICAL constant , *STAR formation , *COMPUTER simulation , *MOLECULAR astrophysics , *COMPACT objects (Astronomy) - Abstract
The standard cosmological model predicts that the first cosmological objects are formed when the age of the universe is a few hundred million years. Recent theoretical studies and numerical simulations consistently suggest that the first objects are very massive primordial stars. We introduce the key physics and explain why the first stars are thought to be massive, rather than to be low-mass stars. The state-of-the-art simulations include all the relevant atomic and molecular physics to follow the thermal evolution of a prestellar gas cloud to very high “stellar” densities. We also show the evolutionary calculation of very massive stars. [ABSTRACT FROM AUTHOR]
- Published
- 2010
- Full Text
- View/download PDF
43. The Dual Role of Atomic and Molecular Astrophysics: Discovery and Data.
- Author
-
Kirby, Kate P.
- Subjects
- *
MOLECULAR astrophysics , *SPECTRUM analysis , *COLLISIONS (Nuclear physics) , *ASTRONOMERS , *PHOTONS , *X-rays - Abstract
Atomic and molecular astrophysics, including both spectroscopy and collision processes, enables astronomers to translate the information carried by photons, collected and energy-analyzed in both ground- and space-based instruments, into understanding and knowledge of diverse astronomical objects. In this paper I focus on the role of atomic and molecular astrophysics (a part of the general field of Laboratory Astrophysics) in both providing overall understanding of new phenomena and contributing sensitive diagnostic probes to use in characterizing astrophysical X-ray sources. [ABSTRACT FROM AUTHOR]
- Published
- 2009
- Full Text
- View/download PDF
44. ITAMP HISTORY: PART III.
- Author
-
Kirby, Kate
- Subjects
ATOMIC physics ,MOLECULAR astrophysics ,X-rays ,CONFERENCES & conventions - Published
- 2009
45. MOLECULAR ASTROPHYSICS WITH THE SPITZER SPACE TELESCOPE: STUDIES OF INTERSTELLAR SHOCKS.
- Author
-
Neufeld, David A.
- Subjects
MOLECULAR astrophysics ,INTERSTELLAR medium ,SPECTROGRAPHS - Published
- 2009
46. ATOMIC AND MOLECULAR PROBES FOR ASTRONOMICAL ENVIRONMENTS.
- Author
-
Lepp, Stephen H.
- Subjects
MOLECULAR astrophysics ,RADIO telescopes ,MOLECULAR theory ,INFRARED spectra ,ASTROPHYSICS - Published
- 2009
47. Millimeter-Wave Spectroscopy of Metal-Bearing Molecules in the ISM.
- Author
-
Ziurys, Lucy M.
- Subjects
- *
INTERSTELLAR medium , *RADIOFREQUENCY spectroscopy , *MILKY Way , *MOLECULAR astrophysics , *ASTRONOMICAL spectroscopy , *STELLAR evolution - Abstract
Over the past thirty years of millimeter astronomy, a great deal has been learned about interstellar molecules and their chemistry. Despite this progress, there are still areas of molecular astrophysics where challenges remain. One of these areas concerns the chemistry and distribution of molecules containing metals. Identifying the carriers of these elements in the interstellar medium, including circumstellar gas, is crucial for the evaluation of dust grain composition, ionization balance, mass loss from evolved stars, and elemental depletions. Over the past decade, the Ziurys group has been actively involved in both the laboratory measurement of the millimeter/sub-millimeter spectra of metal-containing molecules and in radio astronomical searches for these species in the ISM. A wide variety of small, metal-bearing species have been studied in our laboratory in the gas-phase using direct absorption techniques. These compounds include diatomic hydrides, halides, carbides, nitrides, oxides, and sulfides, and the polyatomic amides, hydroxides, acetylides, and cyanides. Some of the species recently studied are CrH (X6Σ+), CaC (X3Σ-), AlSH (X1A′), AlNC (X1Σ+), and CoCN (X 3[uppercase_phi_synonym]i). We have begun to study metal-bearing molecular ions as well (TiCl+: X3[uppercase_phi_synonym]r; VCl+: X4Σ-; FeCO+: X4Σ-; for example), using a new millimeter/sub-millimeter velocity modulation system. A new Fourier transform microwave spectrometer has also just been completed and will be used for laser-ablation investigations of such species. Radio astronomical searches have been made for almost all of these molecules, using the Arizona Radio Observatory’s facilities and the IRAM 30 m telescope. Interestingly, besides the halides, only metal cyanide and isocyanide species have been detected in astronomical sources, and only in circumstellar envelopes of carbon-rich AGB stars. Among the molecules identified are AlNC, MgCN, and KCN. Metal-bearing species have been generally found in the envelope of the carbon star IRC+10216, but some are also present in other circumstellar shells of such objects as CRL2688 and CRL618. Nucleosynthesis occurs in AGB stars, and may produce metals such as sodium and magnesium. Therefore, the metal-bearing molecules detected in AGB envelopes may reflect enhancements in elemental abundances resulting from such nucleosynthesis, rather than cosmic abundances. Such elements would be mixed into the circumstellar shell in the third dredge-up, which also brings carbon to the stellar surface, creating a C-rich envelope. Additional metal-containing molecules need to be observed in AGB shells to verify this connection. These observations await new laboratory spectra. Metal cyanide/isocyanide compounds are the obvious choices for such laboratory work, in particular FeNC. This species has remained elusive, although the spectrum of CrCN has now been measured. © 2006 American Institute of Physics [ABSTRACT FROM AUTHOR]
- Published
- 2006
- Full Text
- View/download PDF
48. Ion Storage Ring Studies of Dissociative Recombination Reactions.
- Author
-
Larsson, Mats and Geppert, Wolf D.
- Subjects
- *
ION recombination , *MOLECULAR astrophysics , *STORAGE rings , *DISSOCIATION (Chemistry) , *CHEMICAL reactions , *LOW temperature plasmas - Abstract
Dissociative recombination of molecular ions with electrons is an important gas-phase process for production of interstellar molecules. Product branching ratios in dissociative recombination have been notoriously difficult to measure in the laboratory. In recent years, the ion storage ring CRYRING in Stockholm has been used to measure branching ratios for astrophysically important molecular ions by means of a grid technique. © 2006 American Institute of Physics [ABSTRACT FROM AUTHOR]
- Published
- 2006
- Full Text
- View/download PDF
49. Interstellar Molecules: The New Frontiers for Molecular Data.
- Author
-
Ziurys, Lucy M. and Apponi, Aldo J.
- Subjects
- *
INTERSTELLAR molecules , *MOLECULAR astrophysics - Abstract
Although over 110 chemical species have been securely identified in the interstellar and circumstellar gas, there are still many data needs for molecular astrophysics. Among these needs are new high-resolution spectroscopic measurements of potential interstellar molecules, in particular organic radicals, metal-bearing molecules, and molecular ions. Ab initio studies that support these experimental investigations are necessary as well. Reaction rate measurements of many ion-molecule, neutral-neutral, and radiative association processes are also essential. [ABSTRACT FROM AUTHOR]
- Published
- 2002
50. LHCb pentaquark as a D¯*Σc - D¯*Σ*c molecular state.
- Author
-
Roca, L., Nieves, J., and Oset, E.
- Subjects
- *
PENTAQUARK , *EXOTIC baryons , *MOLECULAR astrophysics - Abstract
We perform a theoretical analysis of the Λb → J/ΨK- p reaction from where a recent LHCb experiment extracts a Λ(1405) contribution in the K- p spectrum close to threshold and two baryon states of hidden charm in the J/Ψp spectrum. We recall that baryon states of this type have been theoretically predicted matching the mass, width and JP of the experiment; concretely some states built up from the J/ΨN, D¯* Λc, D¯*Σc, D¯Σc,* and D¯*Σc* coupled channels. We assume that the observed narrow state around 4450 MeV has this nature and we are able to describe simultaneously the shapes and relative strength of the the K- p mass distribution close to threshold and the peak of the J/Ψp distribution, with values of the J/Ψp coupling to the resonance in line with the theoretical ones. The nontrivial matching of many properties gives support to a JP = 3/2- assignment to this state and to its nature as a molecular state mostly made of D¯*Σc and D¯*Σc*. [ABSTRACT FROM AUTHOR]
- Published
- 2015
- Full Text
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