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Astronomy and Astrophysics

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https://www.readbyqxmd.com/read/30369620/diagnostic-value-of-far-ir-water-ice-features-in-t-tauri-disks
#1
I Kamp, A Scheepstra, M Min, L Klarmann, P Riviere-Marichalar
Aims: This paper investigates how the far-IR water ice features can be used to infer properties of disks around T Tauri stars and the water ice thermal history. We explore the power of future observations with SOFIA/HIRMES and SPICA's proposed far-IR instrument SAFARI. Methods: A series of detailed radiative transfer disk models around a representative T Tauri star are used to investigate how the far-IR water ice features at 45 and 63 μ m change with key disk properties: disk size, grain sizes, disk dust mass, dust settling, and ice thickness...
September 12, 2018: Astronomy and Astrophysics
https://www.readbyqxmd.com/read/30185991/the-chemistry-of-disks-around-t-tauri-and-herbig-ae-be-stars
#2
Marcelino Agúndez, Evelyne Roueff, Franck Le Petit, Jacques Le Bourlot
Context: Infrared and (sub-)mm observations of disks around T Tauri and Herbig Ae/Be stars point to a chemical differentiation between both types of disks, with a lower detection rate of molecules in disks around hotter stars. Aims: To investigate the underlying causes of the chemical differentiation indicated by observations we perform a comparative study of the chemistry of T Tauri and Herbig Ae/Be disks. This is one of the first studies to compare chemistry in the outer regions of these two types of disks...
August 7, 2018: Astronomy and Astrophysics
https://www.readbyqxmd.com/read/30369619/millimeter-wave-spectra-of-ethyl-isocyanate-and-searches-for-it-in-orion-kl-and-sgr-b2
#3
L Kolesniková, E R Alonso, B Tercero, J Cernicharo, J L Alonso
Context: Relatively high abundances of methyl isocyanate (CH3 NCO), a methyl derivative of isocyanic acid (HNCO), found in the Orion KL and Sgr B2 molecular clouds suggest that its ethyl derivative, ethyl isocyanate (CH3 CH2 NCO), may also be present. Aims: The aim of this work is to provide accurate experimental frequencies of ethyl isocyanate in its ground and excited vibrational states in the millimeter wave region to support searches for it in the interstellar medium...
August 2018: Astronomy and Astrophysics
https://www.readbyqxmd.com/read/30185990/structure-of-photodissociation-fronts-in-star-forming-regions-revealed-by-observations-of-high-j-co-emission-lines-with-herschel
#4
C Joblin, E Bron, C Pinto, P Pilleri, F Le Petit, M Gerin, J Le Bourlot, A Fuente, O Berne, J R Goicoechea, E Habart, M Köhler, D Teyssier, Z Nagy, J Montillaud, C Vastel, J Cernicharo, M Röllig, V Ossenkopf-Okada, E A Bergin
Context: In bright photodissociation regions (PDRs) associated to massive star formation, the presence of dense "clumps" that are immersed in a less dense interclump medium is often proposed to explain the difficulty of models to account for the observed gas emission in high-excitation lines. Aims: We aim at presenting a comprehensive view of the modeling of the CO rotational ladder in PDRs, including the high-J lines that trace warm molecular gas at PDR interfaces...
July 2018: Astronomy and Astrophysics
https://www.readbyqxmd.com/read/30185989/time-dependent-molecular-emission-in-irc-10216
#5
J R Pardo, J Cernicharo, L Velilla Prieto, J P Fonfría, M Agúndez, G Quintana-Lacaci, S Massalkhi, B Tercero, M Gómez-Garrido, P de Vicente, M Guélin, C Kramer, C Marka, D Teyssier, D Neufeld
Context: The variability in IRC+10216, the envelope of the asymptotic giant branch (AGB) star CW Leo, has attracted increasing attention in recent years. Studying the details of this variability in the molecular emission required a systematic observation program. Aims: We aim to reveal and characterize the periodical variability of the rotational lines from several molecules and radicals in IRC+10216, and to compare it with previously reported IR variability. Methods: We carried out systematic monitoring within the ~80 to 116 GHz frequency range with the IRAM 30m telescope...
July 2018: Astronomy and Astrophysics
https://www.readbyqxmd.com/read/29973739/discovery-of-the-elusive-radical-nco-and-confirmation-of-h-2-nco-in-space
#6
N Marcelino, M Agúndez, J Cernicharo, E Roueff, M Tafalla
The isocyanate radical (NCO) is the simplest molecule containing the backbone of the peptide bond, C(=O)-N. This bond has a prebiotic interest since is the one linking two amino acids to form large chains of proteins. It is also present in some organic molecules observed in space such as HNCO, NH2 CHO and CH3 NCO. In this letter we report the first detection in space of NCO towards the dense core L483. We also report the identification of the ion H2 NCO+ , definitively confirming its presence in space, and observations of HNCO, HOCN, and HCNO in the same source...
April 2018: Astronomy and Astrophysics
https://www.readbyqxmd.com/read/29983448/detection-of-interstellar-hcs-and-its-metastable-isomer-hsc-new-pieces-in-the-puzzle-of-sulfur-chemistry
#7
M Agúndez, N Marcelino, J Cernicharo, M Tafalla
We present the first identification in interstellar space of the thioformyl radical (HCS) and its metastable isomer HSC. These species were detected toward the molecular cloud L483 thanks to observations carried out with the IRAM 30m telescope in the λ 3 mm band. We derive beam-averaged column densities of 7 × 1012 cm-2 for HCS and 1.8 × 1011 cm-2 for HSC, which translate to fractional abundances relative to H2 of 2 × 10-10 and 6 × 10-12 , respectively. Although the amount of sulfur locked by these radicals is low, their detection allows to put interesting constraints on the chemistry of sulfur in dark clouds...
March 14, 2018: Astronomy and Astrophysics
https://www.readbyqxmd.com/read/29628518/the-abundance-of-sic-2-in-carbon-star-envelopes-evidence-that-sic-2-is-a-gas-phase-precursor-of-sic-dust
#8
Sarah Massalkhi, M Agúndez, J Cernicharo, L Velilla Prieto, J R Goicoechea, G Quintana-Lacaci, J P Fonfría, J Alcolea, V Bujarrabal
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 Si2 C. To date, the ring molecule SiC2 has been observed in a handful of evolved stars, while SiC and Si2 C have only been detected in the C-star envelope IRC +10216...
March 2018: Astronomy and Astrophysics
https://www.readbyqxmd.com/read/29456257/irc-10-216-in-3-d-morphology-of-a-tp-agb-star-envelope
#9
M Guélin, N A Patel, M Bremer, J Cernicharo, A Castro-Carrizo, J Pety, J P Fonfría, M Agúndez, M Santander-García, G Quintana-Lacaci, L Velilla Prieto, R Blundell, P Thaddeus
During their late pulsating phase, AGB stars expel most of their mass in the form of massive dusty envelopes, an event that largely controls the composition of interstellar matter. The envelopes, however, are distant and opaque to visible and NIR radiation: their structure remains poorly known and the mass-loss process poorly understood. Millimeter-wave interferometry, which combines the advantages of longer wavelength, high angular resolution and very high spectral resolution is the optimal investigative tool for this purpose...
February 2018: Astronomy and Astrophysics
https://www.readbyqxmd.com/read/29456256/clustering-the-orion-b-giant-molecular-cloud-based-on-its-molecular-emission
#10
Emeric Bron, Chloé Daudon, Jérôme Pety, François Levrier, Maryvonne Gerin, Pierre Gratier, Jan H Orkisz, Viviana Guzman, Sébastien Bardeau, Javier R Goicoechea, Harvey Liszt, Karin Öberg, Nicolas Peretto, Albrecht Sievers, Pascal Tremblin
Context: Previous attempts at segmenting molecular line maps of molecular clouds have focused on using position-position-velocity data cubes of a single molecular line to separate the spatial components of the cloud. In contrast, wide field spectral imaging over a large spectral bandwidth in the (sub)mm domain now allows one to combine multiple molecular tracers to understand the different physical and chemical phases that constitute giant molecular clouds (GMCs). Aims: We aim at using multiple tracers (sensitive to different physical processes and conditions) to segment a molecular cloud into physically/chemically similar regions (rather than spatially connected components), thus disentangling the different physical/chemical phases present in the cloud...
February 2018: Astronomy and Astrophysics
https://www.readbyqxmd.com/read/30078846/laboratory-measurements-and-astronomical-search-for-cyanomethanimine
#11
M Melosso, A Melli, C Puzzarini, C Codella, L Spada, L Dore, C Degli Esposti, B Lefloch, R Bachiller, C Ceccarelli, J Cernicharo, V Barone
Context: C-cyanomethanimine (HNCHCN), existing in the two Z and E isomeric forms, is a key prebiotic molecule, but, so far, only the E isomer has been detected toward the massive star-forming region. Sagittarius B2(N) using transitions in the radio wavelength domain. Aims: With the aim of detecting HNCHCN in Sun-like-star forming regions, the laboratory investigation of its rotational spectrum has been extended to the millimeter-/submillimeter-wave (mm-/submm-) spectral window in which several unbiased spectral surveys have been already carried out...
January 2018: Astronomy and Astrophysics
https://www.readbyqxmd.com/read/29983447/rotational-spectrum-of-methoxyamine-up-to-480-ghz-a-laboratory-study-and-astronomical-search
#12
L Kolesniková, B Tercero, E R Alonso, J-C Guillemin, J Cernicharo, J L Alonso
Aims: Methoxyamine is a potential interstellar amine that has been predicted by gas-grain chemical models for the formation of complex molecules. The aim of this work is to provide direct experimental frequencies of its ground-vibrational state in the millimeter- and submillimeter-wave regions to achieve its detection in the interstellar medium. Methods: Methoxyamine was chemically liberated from its hydrochloride salt, and its rotational spectrum was recorded at room temperature from 75 to 480 GHz using the millimeter-wave spectrometer in Valladolid...
January 2018: Astronomy and Astrophysics
https://www.readbyqxmd.com/read/29277841/using-radio-astronomical-receivers-for-molecular-spectroscopic-characterization-in-astrochemical-laboratory-simulations-a-proof-of-concept
#13
I Tanarro, B Alemán, P de Vicente, J D Gallego, J R Pardo, G Santoro, K Lauwaet, F Tercero, A Díaz-Pulido, E Moreno, M Agúndez, J R Goicoechea, J M Sobrado, J A López, L Martínez, J L Doménech, V J Herrero, J M Hernández, R J Peláez, J A López-Pérez, J Gómez-González, J L Alonso, E Jiménez, D Teyssier, K Makasheva, M Castellanos, C Joblin, J A Martín-Gago, J Cernicharo
We present a proof of concept on the coupling of radio astronomical receivers and spectrometers with chemical reactors and the performances of the resulting setup for spectroscopy and chemical simulations in laboratory astrophysics. Several experiments including cold plasma generation and UV photochemistry were performed in a 40 cm long gas cell placed in the beam path of the Aries 40 m radio telescope receivers operating in the 41-49 GHz frequency range interfaced with fast Fourier transform spectrometers providing 2 GHz bandwidth and 38 kHz resolution...
January 2018: Astronomy and Astrophysics
https://www.readbyqxmd.com/read/29151609/clues-to-nacn-formation
#14
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
#15
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
#16
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
#17
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, CH3 SiH3 , from observations of ten rotational transitions between 80 and 350 GHz ( J u 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 (SiH3 CN), 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
#18
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 the13 CO 1→0, C18 O 1→0, NH2 D 11,1 a →10,1 s , 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
#19
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
#20
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
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