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Astronomy and Astrophysics

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https://read.qxmd.com/read/30595605/the-millimeter-wave-spectrum-of-methyl-ketene-and-the-astronomical-search-for-it
#1
C Bermúdez, B Tercero, R A Motiyenko, L Margulès, J Cernicharo, Y Ellinger, J-C Guillemin
Context: The analysis of isomeric species of a compound observed in the interstellar medium (ISM) is a useful tool to understand the chemistry of complex organic molecules. It could, likewise, assist in the detection of new species. Aims: Our goal consists in analyzing one of the two most stable species of the C3 H4 O family, methyl ketene, whose actual rotational parameters are not precise enough to allow its detection in the ISM. The obtained parameters will be used to search for it in the high-mass star-forming regions Orion KL and Sagittarius B2, as well as in the cold dark clouds TMC-1 in the Taurus Molecular Cloud and Barnard 1 (B1-b)...
November 12, 2018: Astronomy and Astrophysics
https://read.qxmd.com/read/30555173/laboratory-rotational-spectrum-and-astronomical-search-for-methoxyacetaldehyde
#2
L Kolesniková, I Peña, E R Alonso, B Tercero, J Cernicharo, S Mata, J L Alonso
Context: Methoxyacetaldehyde belongs to a group of structural isomers with the general formula C3 H6 O2 , of which methyl acetate and ethyl formate are known interstellar molecules. Rotational data available for methoxyacetaldehyde are limited to 40 GHz, which makes predictions at higher frequencies rather uncertain. Aims: The aim of this work is to provide accurate experimental frequencies of methoxyacetaldehyde in the millimeter-wave region to support its detection in the interstellar medium...
November 8, 2018: Astronomy and Astrophysics
https://read.qxmd.com/read/30473586/through-the-magnifying-glass-alma-acute-viewing-of-the-intricate-nebular-architecture-of-oh231-8-4-2
#3
C Sánchez Contreras, J Alcolea, V Bujarrabal, A Castro-Carrizo, L Velilla Prieto, M Santander-García, G Quintana-Lacaci, J Cernicharo
We present continuum and molecular line emission ALMA observations of OH 231.8+4.2, a well studied bipolar nebula around an asymptotic giant branch (AGB) star. The high angular resolution <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mrow> <mml:mo>(</mml:mo> <mml:mo>∼</mml:mo> <mml:msubsup> <mml:mn>0</mml:mn> <mml:mo>·</mml:mo> <mml:mrow> <mml:mo>″</mml:mo> </mml:mrow> </mml:msubsup> <mml:mn>2</mml:mn> <mml:mtext>-</mml:mtext> <mml:msubsup> <mml:mn>0</mml:mn> <mml:mo>·</mml:mo> <mml:mrow> <mml:mo>″</mml:mo> </mml:mrow> </mml:msubsup> <mml:mn>3</mml:mn> <mml:mo>)</mml:mo> </mml:mrow> </mml:math> and sensitivity of our ALMA maps provide the most detailed and accurate description of the overall nebular structure and kinematics of this object to date...
October 23, 2018: Astronomy and Astrophysics
https://read.qxmd.com/read/30429617/high-speed-molecular-cloudlets-around-the-galactic-center-s-supermassive-black-hole
#4
Javier R Goicoechea, Jerome Pety, Edwige Chapillon, José Cernicharo, Maryvonne Gerin, Cinthya Herrera, Miguel A Requena-Torres, Miriam G Santa-Maria
We present 1″-resolution ALMA observations of the circumnuclear disk (CND) and the interstellar environment around Sgr A*. The images unveil the presence of small spatial scale 12 CO ( J =3-2) molecular "cloudlets" (≲20,000 AU size) within the central parsec of the Milky Way, in other words, inside the cavity of the CND, and moving at high speeds, up to 300 km s-1 along the line-of-sight. The 12 CO-emitting structures show intricate morphologies: extended and filamentary at high negative-velocities (vLSR ≲-150 km s-1 ), more localized and clumpy at extreme positive-velocities (vLSR ≳+200 km s-1 )...
October 11, 2018: Astronomy and Astrophysics
https://read.qxmd.com/read/30429616/irc-10216-as-a-spectroscopic-laboratory-improved-rotational-constants-for-sic-2-its-isotopologues-and-si-2-c
#5
J Cernicharo, M Guélin, M Agúndez, J R Pardo, S Massalkhi, J P Fonfría, L Velilla Prieto, G Quintana-Lacaci, N Marcelino, C Marka, S Navarro, C Kramer
This work presents a detailed analysis of the laboratory and astrophysical spectral data available for 28 SiC2 , 29 SiC2 ,30 SiC2 , Si13 CC, and Si2 C. New data on the rotational lines of these species between 70 and 350 GHz have been obtained with high spectral resolution (195 kHz) with the IRAM 30m telescope in the direction of the circumstellar envelope IRC +10216. Frequency measurements can reach an accuracy of 50 kHz for features observed with a good signal to noise ratio. From the observed astrophysical lines and the available laboratory data new rotational and centrifugal distortion constants have been derived for all the isotopologues of SiC2 , allowing to predict their spectrum with high accuracy in the millimeter and submillimeter domains...
October 2018: Astronomy and Astrophysics
https://read.qxmd.com/read/30473585/revisiting-the-case-of-r-monocerotis-is-co-removed-at-r-20-au-%C3%A2
#6
T Alonso-Albi, P Riviere-Marichalar, A Fuente, S Pacheco-Vázquez, B Montesinos, R Bachiller, S P Treviño-Morales
Context: To our knowledge, R Mon is the only B0 star in which a gaseous Keplerian disk has been detected. However, there is some controversy about the spectral type of R Mon. Some authors propose that it could be a later B8e star, where disks are more common. Aims: Our goal is to re-evaluate the R Mon spectral type and characterize its protoplanetary disk. Methods: The spectral type of R Mon has been re-evaluated using the available continuum data and UVES emission lines...
September 12, 2018: Astronomy and Astrophysics
https://read.qxmd.com/read/30369620/diagnostic-value-of-far-ir-water-ice-features-in-t-tauri-disks
#7
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://read.qxmd.com/read/30185991/the-chemistry-of-disks-around-t-tauri-and-herbig-ae-be-stars
#8
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://read.qxmd.com/read/30369619/millimeter-wave-spectra-of-ethyl-isocyanate-and-searches-for-it-in-orion-kl-and-sgr-b2
#9
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://read.qxmd.com/read/30185990/structure-of-photodissociation-fronts-in-star-forming-regions-revealed-by-observations-of-high-j-co-emission-lines-with-herschel
#10
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://read.qxmd.com/read/30185989/time-dependent-molecular-emission-in-irc-10216
#11
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://read.qxmd.com/read/29973739/discovery-of-the-elusive-radical-nco-and-confirmation-of-h-2-nco-in-space
#12
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://read.qxmd.com/read/29983448/detection-of-interstellar-hcs-and-its-metastable-isomer-hsc-new-pieces-in-the-puzzle-of-sulfur-chemistry
#13
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://read.qxmd.com/read/29628518/the-abundance-of-sic-2-in-carbon-star-envelopes-evidence-that-sic-2-is-a-gas-phase-precursor-of-sic-dust
#14
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://read.qxmd.com/read/29456257/irc-10-216-in-3-d-morphology-of-a-tp-agb-star-envelope
#15
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://read.qxmd.com/read/29456256/clustering-the-orion-b-giant-molecular-cloud-based-on-its-molecular-emission
#16
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://read.qxmd.com/read/30078846/laboratory-measurements-and-astronomical-search-for-cyanomethanimine
#17
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://read.qxmd.com/read/29983447/rotational-spectrum-of-methoxyamine-up-to-480-ghz-a-laboratory-study-and-astronomical-search
#18
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://read.qxmd.com/read/29277841/using-radio-astronomical-receivers-for-molecular-spectroscopic-characterization-in-astrochemical-laboratory-simulations-a-proof-of-concept
#19
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://read.qxmd.com/read/29151609/clues-to-nacn-formation
#20
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
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