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Astronomy and Astrophysics

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https://www.readbyqxmd.com/read/29151609/clues-to-nacn-formation
#1
G Quintana-Lacaci, J Cernicharo, L Velilla Prieto, M Agúndez, A Castro-Carrizo, J P Fonfría, S Massalkhi, J R Pardo
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...
November 2017: Astronomy and Astrophysics
https://www.readbyqxmd.com/read/29151608/the-eso-diffuse-interstellar-bands-large-exploration-survey-edibles-i-project-description-survey-sample-and-quality-assessment
#2
Nick L J Cox, Jan Cami, Amin Farhang, Jonathan Smoker, Ana Monreal-Ibero, Rosine Lallement, Peter J Sarre, Charlotte C M Marshall, Keith T Smith, Christopher J Evans, Pierre Royer, Harold Linnartz, Martin A Cordiner, Christine Joblin, Jacco Th van Loon, Bernard H Foing, Neil H Bhatt, Emeric Bron, Meriem Elyajouri, Alex de Koter, Pascale Ehrenfreund, Atefeh Javadi, Lex Kaper, Habib G Khosroshadi, Mike Laverick, Franck Le Petit, Giacomo Mulas, Evelyne Roueff, Farid Salama, Marco Spaans
The carriers of the diffuse interstellar bands (DIBs) are largely unidentified molecules ubiquitously present in the interstellar medium (ISM). After decades of study, two strong and possibly three weak near-infrared DIBs have recently been attributed to the [Formula: see text] fullerene based on observational and laboratory measurements. There is great promise for the identification of the over 400 other known DIBs, as this result could provide chemical hints towards other possible carriers. In an effort to systematically study the properties of the DIB carriers, we have initiated a new large-scale observational survey: the ESO Diffuse Interstellar Bands Large Exploration Survey (EDIBLES)...
October 2017: Astronomy and Astrophysics
https://www.readbyqxmd.com/read/29142329/evidence-for-disks-at-an-early-stage-in-class-0-protostars
#3
M Gerin, J Pety, B Commerçon, A Fuente, J Cernicharo, N Marcelino, A Ciardi, D C Lis, E Roueff, H A Wootten, E Chapillon
Aims: The formation epoch of protostellar disks is debated because of the competing roles of rotation, turbulence, and magnetic fields in the early stages of low-mass star formation. Magnetohydrodynamics simulations of collapsing cores predict that rotationally supported disks may form in strongly magnetized cores through ambipolar diffusion or misalignment between the rotation axis and the magnetic field orientation. Detailed studies of individual sources are needed to cross check the theoretical predictions...
October 2017: Astronomy and Astrophysics
https://www.readbyqxmd.com/read/29142328/discovery-of-methyl-silane-and-confirmation-of-silyl-cyanide-in-irc-10216
#4
J Cernicharo, M Agúndez, L Velilla Prieto, M Guélin, J R Pardo, C Kahane, C Marka, C Kramer, S Navarro, G Quintana-Lacaci, J P Fonfría, N Marcelino, B Tercero, E Moreno, S Massalkhi, M Santander-García, M C McCarthy, C A Gottlieb, J L Alonso
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...
October 2017: Astronomy and Astrophysics
https://www.readbyqxmd.com/read/29093600/chemical-segregation-in-the-young-protostars-barnard-1b-n-and-s-evidence-of-pseudo-disk-rotation-in-barnard-1b-s
#5
A Fuente, M Gerin, J Pety, B Commerçon, M Agúndez, J Cernicharo, N Marcelino, E Roueff, D C Lis, H A Wootten
The extremely young Class 0 object B1b-S and the first hydrostatic core (FSHC) candidate, B1b-N, provide a unique opportunity to study the chemical changes produced in the elusive transition from the prestellar core to the protostellar phase. We present 40"×70" images of Barnard 1b in the (13)CO 1→0, C(18)O 1→0, NH2D 11,1a→10,1s, and SO 32→21 lines obtained with the NOEMA interferometer. The observed chemical segregation allows us to unveil the physical structure of this young protostellar system down to scales of ∼500 au...
October 2017: Astronomy and Astrophysics
https://www.readbyqxmd.com/read/28989177/-cii-emission-from-l1630-in-the-orion-b-molecular-cloud
#6
C H M Pabst, J R Goicoechea, D Teyssier, O Berné, B B Ochsendorf, M G Wolfire, R D Higgins, D Riquelme, C Risacher, J Pety, F Le Petit, E Roueff, E Bron, A G G M Tielens
CONTEXT: L1630 in the Orion B molecular cloud, which includes the iconic Horsehead Nebula, illuminated by the star system σ Ori, is an example of a photodissociation region (PDR). In PDRs, stellar radiation impinges on the surface of dense material, often a molecular cloud, thereby inducing a complex network of chemical reactions and physical processes. AIMS: Observations toward L1630 allow us to study the interplay between stellar radiation and a molecular cloud under relatively benign conditions, that is, intermediate densities and an intermediate UV radiation field...
October 2017: Astronomy and Astrophysics
https://www.readbyqxmd.com/read/29142327/the-circumstellar-envelope-around-the-s-type-agb-star-w-aql-effects-of-an-eccentric-binary-orbit
#7
S Ramstedt, S Mohamed, W H T Vlemmings, T Danilovich, M Brunner, E De Beck, E M L Humphreys, M Lindqvist, M Maercker, H Olofsson, F Kerschbaum, G Quintana-Lacaci
Context: Recent observations at subarcsecond resolution, now possible also at submillimeter wavelengths, have shown intricate circumstellar structures around asymptotic giant branch (AGB) stars, mostly attributed to binary interaction. The results presented here are part of a larger project aimed at investigating the effects of a binary companion on the morphology of circumstellar envelopes (CSEs) of AGB stars. Aims: AGB stars are characterized by intense stellar winds that build CSEs around the stars...
September 21, 2017: Astronomy and Astrophysics
https://www.readbyqxmd.com/read/29151607/zeeman-effect-in-sulfur-monoxide-a-tool-to-probe-magnetic-fields-in-star-forming-regions
#8
Gabriele Cazzoli, Valerio Lattanzi, Sonia Coriani, Jürgen Gauss, Claudio Codella, Andrés Asensio Ramos, José Cernicharo, Cristina Puzzarini
Context: Magnetic fields play a fundamental role in star formation processes and the best method to evaluate their intensity is to measure the Zeeman effect of atomic and molecular lines. However, a direct measurement of the Zeeman spectral pattern from interstellar molecular species is challenging due to the high sensitivity and high spectral resolution required. So far, the Zeeman effect has been detected unambiguously in star forming regions for very few non-masing species, such as OH and CN...
September 2017: Astronomy and Astrophysics
https://www.readbyqxmd.com/read/29151606/a-spectroscopic-survey-of-orion-kl-between-41-5-and-50-ghz
#9
J R Rizzo, B Tercero, J Cernicharo
Context: The nearby massive star-forming region Orion KL is one of the richest molecular reservoirs known in our Galaxy. The region hosts newly formed protostars, and the strong interaction between their radiation and their outflows with the environment results in a series of complex chemical processes leading to a high diversity of interstellar tracers. The region is therefore one of the most frequently observed sources, and the site where many molecular species have been discovered for the first time...
September 2017: Astronomy and Astrophysics
https://www.readbyqxmd.com/read/28867822/detection-of-buckminsterfullerene-emission-in-the-diffuse-interstellar-medium
#10
O Berné, N L J Cox, G Mulas, C Joblin
Emission of fullerenes in their infrared vibrational bands has been detected in space near hot stars. The proposed attribution of the diffuse interstellar bands at 9577 and 9632 Å to electronic transitions of the buckminsterfullerene cation (i.e. [Formula: see text]) was recently supported by new laboratory data, confirming the presence of this species in the diffuse interstellar medium (ISM). In this letter, we present the detection, also in the diffuse ISM, of the 17.4 and 18.9 μm emission bands commonly attributed to vibrational bands of neutral C60...
September 2017: Astronomy and Astrophysics
https://www.readbyqxmd.com/read/29093599/herschel-survey-and-modelling-of-externally-illuminated-photoevaporating-protoplanetary-disks
#11
J Champion, O Berné, S Vicente, I Kamp, F Le Petit, A Gusdorf, C Joblin, J R Goicoechea
Context: Protoplanetary disks undergo substantial mass-loss by photoevaporation, a mechanism which is crucial to their dynamical evolution. However, the processes regulating the gas energetics have not been well constrained by observations so far. Aims: We aim at studying the processes involved in disk photoevaporation when it is driven by far-UV photons (i.e. 6 < E < 13.6 eV). Methods: We present a unique Herschel survey and new ALMA observations of four externally-illuminated photoevaporating disks (a...
August 2017: Astronomy and Astrophysics
https://www.readbyqxmd.com/read/29142326/complex-organic-molecules-in-strongly-uv-irradiated-gas
#12
S Cuadrado, J R Goicoechea, J Cernicharo, A Fuente, J Pety, B Tercero
We investigate the presence of complex organic molecules (COMs) in strongly UV-irradiated interstellar molecular gas. We have carried out a complete millimetre (mm) line survey using the IRAM 30 m telescope towards the edge of the Orion Bar photodissociation region (PDR), close to the H2 dissociation front, a position irradiated by a very intense far-UV (FUV) radiation field. These observations have been complemented with 8.5″ resolution maps of the H2CO JKa,Kc = 51,5 → 41,4 and C(18)O J = 3 → 2 emission at 0...
July 2017: Astronomy and Astrophysics
https://www.readbyqxmd.com/read/29151605/sub-arcsecond-imaging-of-the-water-emission-in-arp-220
#13
S König, S Martín, S Muller, J Cernicharo, K Sakamoto, L K Zschaechner, E M L Humphreys, T Mroczkowski, M Krips, M Galametz, S Aalto, W H T Vlemmings, J Ott, D S Meier, A Fuente, S García-Burillo, R Neri
Aims: Extragalactic observations of water emission can provide valuable insights into the excitation of the interstellar medium. In particular they allow us to investigate the excitation mechanisms in obscured nuclei, i.e. whether an active galactic nucleus or a starburst dominate. Methods: We use sub-arcsecond resolution observations to tackle the nature of the water emission in Arp 220. ALMA Band 5 science verification observations of the 183 GHz H2O 313-220 line, in conjunction with new ALMA Band 7 H2O 515-422 data at 325 GHz, and supplementary 22 GHz H2O 616 - 523 VLA observations, are used to better constrain the parameter space in the excitation modelling of the water lines...
June 2017: Astronomy and Astrophysics
https://www.readbyqxmd.com/read/28690335/spatially-resolved-images-of-reactive-ions-in-the-orion-bar-%C3%A2-%C3%A2
#14
Javier R Goicoechea, Sara Cuadrado, Jérôme Pety, Emeric Bron, John H Black, José Cernicharo, Edwige Chapillon, Asunción Fuente, Maryvonne Gerin
We report high angular resolution (4.9″×3.0″) images of reactive ions SH(+), HOC(+), and SO(+) toward the Orion Bar photodissociation region (PDR). We used ALMA-ACA to map several rotational lines at 0.8 mm, complemented with multi-line observations obtained with the IRAM 30 m telescope. The SH(+) and HOC(+) emission is restricted to a narrow layer of 2″- to 10″-width (≈800 to 4000 AU depending on the assumed PDR geometry) that follows the vibrationally excited [Formula: see text] emission. Both ions efficiently form very close to the H/H2 transition zone, at a depth of Av≲1 mag into the neutral cloud, where abundant C(+), S(+), and [Formula: see text] coexist...
May 2017: Astronomy and Astrophysics
https://www.readbyqxmd.com/read/28469283/the-growth-of-carbon-chains-in-irc-10216-mapped-with-alma
#15
M Agúndez, J Cernicharo, G Quintana-Lacaci, A Castro-Carrizo, L Velilla Prieto, N Marcelino, M Guélin, C Joblin, J A Martín-Gago, C A Gottlieb, N A Patel, M C McCarthy
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″...
May 2017: Astronomy and Astrophysics
https://www.readbyqxmd.com/read/28260804/spatial-distribution-of-fir-rotationally-excited-ch-and-oh-emission-lines-in-the-orion-bar-pdr
#16
A Parikka, E Habart, J Bernard-Salas, J R Goicoechea, A Abergel, P Pilleri, E Dartois, C Joblin, M Gerin, B Godard
CONTEXT: The methylidyne cation (CH(+)) and hydroxyl (OH) are key molecules in the warm interstellar chemistry, but their formation and excitation mechanisms are not well understood. Their abundance and excitation are predicted to be enhanced by the presence of vibrationally excited H2 or hot gas (~500-1000 K) in photodissociation regions with high incident FUV radiation field. The excitation may also originate in dense gas (> 10(5) cm(-3)) followed by nonreactive collisions with H2, H, and electrons...
March 2017: Astronomy and Astrophysics
https://www.readbyqxmd.com/read/28190887/alma-compact-array-observations-of-the-fried-egg-nebula-evidence-for-large-scale-asymmetric-mass-loss-from-the-yellow-hypergiant-iras-17163-3907
#17
S H J Wallström, E Lagadec, S Muller, J H Black, N L J Cox, R Galván-Madrid, K Justtanont, S Longmore, H Olofsson, R D Oudmaijer, G Quintana-Lacaci, R Szczerba, W Vlemmings, H van Winckel, A Zijlstra
Yellow hypergiants are rare and represent a fast evolutionary stage of massive evolved stars. That evolutionary phase is characterised by a very intense mass loss, the understanding of which is still very limited. Here we report ALMA Compact Array observations of a 50″-mosaic toward the Fried Egg nebula, around one of the few Galactic yellow hypergiants IRAS 17163-3907. The emission from the (12)CO J=2-1 line, H30α recombination line, and continuum is imaged at a resolution of ~8″, revealing the morphology of the molecular environment around the star...
January 10, 2017: Astronomy and Astrophysics
https://www.readbyqxmd.com/read/28008188/alma-high-spatial-resolution-observations-of-the-dense-molecular-region-of-ngc-6302
#18
M Santander-García, V Bujarrabal, J Alcolea, A Castro-Carrizo, C Sánchez Contreras, G Quintana-Lacaci, R L M Corradi, R Neri
CONTEXT: The mechanism behind the shaping of bipolar planetary nebulae is still poorly understood. It is becoming increasingly clear that the main agents must operate at their innermost regions, where a significant equatorial density enhancement should be present and related to the collimation of light and jet launching from the central star preferentially towards the polar directions. Most of the material in this equatorial condensation must be lost during the asymptotic giant branch as stellar wind and later released from the surface of dust grains to the gas phase in molecular form...
January 2017: Astronomy and Astrophysics
https://www.readbyqxmd.com/read/28008187/the-millimeter-iram-30-m-line-survey-toward-ik-tau
#19
L Velilla Prieto, C Sánchez Contreras, J Cernicharo, M Agúndez, G Quintana-Lacaci, V Bujarrabal, J Alcolea, C Balança, F Herpin, K M Menten, F Wyrowski
AIMS: We aim to investigate the physical and chemical properties of the molecular envelope of the oxygen-rich AGB star IK Tau. METHODS: We carried out a millimeter wavelength line survey between ~79 and 356 GHz with the IRAM-30 m telescope. We analysed the molecular lines detected in IK Tau using the population diagram technique to derive rotational temperatures and column densities. We conducted a radiative transfer analysis of the SO2 lines, which also helped us to verify the validity of the approximated method of the population diagram for the rest of the molecules...
January 2017: Astronomy and Astrophysics
https://www.readbyqxmd.com/read/28003686/trans-cis-molecular-photoswitching-in-interstellar-space
#20
S Cuadrado, J R Goicoechea, O Roncero, A Aguado, B Tercero, J Cernicharo
As many organic molecules, formic acid (HCOOH) has two conformers (trans and cis). The energy barrier to internal conversion from trans to cis is much higher than the thermal energy available in molecular clouds. Thus, only the most stable conformer (trans) is expected to exist in detectable amounts. We report the first interstellar detection of cis-HCOOH. Its presence in ultraviolet (UV) irradiated gas exclusively (the Orion Bar photodissociation region), with a low trans-to-cis abundance ratio of 2.8 ± 1...
December 2016: Astronomy and Astrophysics
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