scholarly journals Submillimeter spectroscopy and astronomical searches of vinyl mercaptan, C2H3SH

2019 ◽  
Vol 623 ◽  
pp. A167 ◽  
Author(s):  
M.-A. Martin-Drumel ◽  
K. L. K. Lee ◽  
A. Belloche ◽  
O. Zingsheim ◽  
S. Thorwirth ◽  
...  
Keyword(s):  
Vinyl Alcohol ◽  
Spectroscopic Constants ◽  
Experimental Investigations ◽  
Rotational Spectrum ◽  
Test Bed ◽  
Frequency Multiplication ◽  
Star Forming ◽  
Astronomical Surveys ◽  
Radiofrequency Discharge ◽  
Upper Limits

Context. New laboratory investigations of the rotational spectrum of postulated astronomical species are essential to support the assignment and analysis of current astronomical surveys. In particular, considerable interest surrounds sulfur analogs of oxygen-containing interstellar molecules and their isomers. Aims. To enable reliable interstellar searches of vinyl mercaptan, the sulfur-containing analog to the astronomical species vinyl alcohol, we investigated its pure rotational spectrum at millimeter wavelengths. Methods. We extended the pure rotational investigation of the two isomers syn and anti vinyl mercaptan to the millimeter domain using a frequency-multiplication spectrometer. The species were produced by a radiofrequency discharge in 1,2-ethanedithiol. Additional transitions were remeasured in the centimeter band using Fourier-transform microwave spectroscopy to better determine rest frequencies of transitions with low-J and low-Ka values. Experimental investigations were supported by quantum chemical calculations on the energetics of both the [C2,H4,S] and [C2,H4,O] isomeric families. Interstellar searches for both syn and anti vinyl mercaptan as well as vinyl alcohol were performed in the EMoCA spectral line survey carried out toward Sgr B2(N2) with ALMA. Results. Highly accurate experimental frequencies (to better than 100 kHz accuracy) for both syn and anti isomers of vinyl mercaptan are measured up to 250 GHz; these deviate considerably from predictions based on extrapolation of previous microwave measurements. Reliable frequency predictions of the astronomically most interesting millimeter-wave lines for these two species can now be derived from the best-fit spectroscopic constants. From the energetic investigations, the four lowest singlet isomers of the [C2,H4,S] family are calculated to be nearly isoenergetic, which makes this family a fairly unique test bed for assessing possible reaction pathways. Upper limits for the column density of syn and anti vinyl mercaptan are derived toward the extremely molecule-rich star-forming region Sgr B2(N2) enabling comparison with selected complex organic molecules.

scholarly journals Rotational spectroscopy of imidazole: improved rest frequencies for astrophysical searches

2019 ◽  
Vol 628 ◽  
pp. A53
Author(s):  
B. M. Giuliano ◽  
L. Bizzocchi ◽  
A. Pietropolli Charmet ◽  
B. E. Arenas ◽  
A. L. Steber ◽  
...  
Keyword(s):  
Spectroscopic Constants ◽  
Rotational Spectrum ◽  
Star Forming ◽  
Star Forming Regions ◽  
Ring Compounds ◽  
Molecular Core ◽  
Wave Region ◽  
Centrifugal Distortion Constants ◽  
High Level ◽  
The University

Context. Organic ring compounds play a key role in terrestrial biochemistry, and they were also most likely pivotal ingredients in Earth’s prebiotic chemistry. The five-membered ring imidazole, c-C3N2H4, is a substructure of fundamental biological molecules such as the purine nucleobases and the amino acid histidine. An unsuccessful search for imidazole in a sample of cold-core clouds and massive star-forming regions was performed almost 40 years ago. At that time, the spectroscopic knowledge of this species was scarce: the existing laboratory study was limited to the centimetre-wave region, and the precision of the rest frequencies in the millimetre regime was not adequate. Aims. The goal of the present work is to perform a comprehensive investigation of the rotational spectrum of imidazole in its ground vibrational state from the microwave region to the 1 mm wavelength regime. Methods. The rotational spectrum of imidazole was recorded in selected frequency regions from 2 to 295 GHz. These intervals were covered using various broadband spectrometers developed at DESY (Hamburg) and at the University of Virginia. High-level ab initio calculations were performed to obtain reliable estimates of the quartic and sextic centrifugal distortion constants. We used the EMoCA imaging spectral line survey to search for imidazole towards the hot molecular core Sgr B2(N2). Results. About 700 rotational transitions spanning a J interval from 0 to 59 and Kc interval from 0 to 30 were analysed using the Watson S-reduced Hamiltonian. These new data allowed the determination of a much extended set of spectroscopic parameters for imidazole in its vibrational ground state. The improved spectral data allow us to set an upper limit to the column density of imidazole in Sgr B2(N2). Its non-detection implies that it is at least 3400 times less abundant than ethyl cyanide in this source. Conclusions. With the new set of spectroscopic constants, it has been possible to compute reliable rest frequencies at millimetre wavelengths. We suggest a search for imidazole towards TMC-1, where the aromatic molecule benzonitrile was recently detected.

scholarly journals Submillimeter-wave spectroscopy and the radio-astronomical investigation of propynethial (HC≡CCHS)

2020 ◽  
Vol 642 ◽  
pp. A206 ◽  
Author(s):  
L. Margulès ◽  
B. A. McGuire ◽  
C. J. Evans ◽  
R. A. Motiyenko ◽  
A. Remijan ◽  
...  
Keyword(s):  
Rotational Spectrum ◽  
Star Forming ◽  
Rotational Spectra ◽  
Dark Clouds ◽  
Star Forming Regions ◽  
Quantum Numbers ◽  
Good Target ◽  
Upper Limits ◽  
Unambiguous Detection ◽  
Sulfur Containing

Context. The majority of sulfur-containing molecules detected in the interstellar medium (ISM) are analogs of oxygen-containing compounds. Propynal was detected in the ISM in 1988, hence propynethial, its sulfur derivative, is a good target for an ISM search. Aims. Our aim is to measure the rotational spectrum of propynethial and use those measurements to search for this species in the ISM. To date, measurements of the rotational spectra of propynethial have been limited to a small number or transitions below 52 GHz. The extrapolation of the prediction to lines in the milimeter-wave domain is inaccurate and does not provide data to permit an unambiguous detection. Methods. The rotational spectrum was re-investigated up to 630 GHz. Using the new prediction lines of propynethial, as well as the related propynal, a variety of astronomical sources were searched, including star-forming regions and dark clouds. Conclusions. A total of 3288 transitions were newly assigned and fit together with those from previous studies, reaching quantum numbers up to J = 107 and Ka = 24. Watson’s symmetric top Hamiltonian in the Ir representation was used for the analysis, because the molecule is very close to the prolate limit. The search for propynethial resulted in a non-detection; upper limits to the column density were derived in each source.

scholarly journals Rotational spectrum of methoxyamine up to 480 GHz: a laboratory study and astronomical search

2017 ◽  
Vol 609 ◽  
pp. A24 ◽  
Author(s):  
L. Kolesniková ◽  
B. Tercero ◽  
E. R. Alonso ◽  
J.-C. Guillemin ◽  
J. Cernicharo ◽  
...  
Keyword(s):  
Internal Rotation ◽  
Room Temperature ◽  
Submillimeter Wave ◽  
Spectroscopic Constants ◽  
Rotational Spectrum ◽  
Stable Conformer ◽  
Complex Molecules ◽  
Methyl Group ◽  
Chemical Models ◽  
Upper Limits

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. Many observed transitions revealedA−Esplitting caused by the internal rotation of the methyl group, which had to be treated with specific internal rotation codes.Results.Over 400 lines were newly assigned for the most stable conformer of methoxyamine, and a precise set of spectroscopic constants was obtained. Spectral features of methoxyamine were then searched for in the Orion KL, Sgr B2, B1-b, and TMC-1 molecular clouds. Upper limits to the column density of methoxyamine were derived.

scholarly journals Millimeter- and submillimeter-wave spectroscopy of thioformamide and interstellar search toward Sgr B2(N)

2020 ◽  
Vol 642 ◽  
pp. A29 ◽  
Author(s):  
R. A. Motiyenko ◽  
A. Belloche ◽  
R. T. Garrod ◽  
L. Margulès ◽  
H. S. P. Müller ◽  
...  
Keyword(s):  
Interstellar Medium ◽  
Rotational Transition ◽  
High Mass ◽  
Mass Star ◽  
Rotational Spectrum ◽  
Star Forming ◽  
Preferential Formation ◽  
Upper Limits ◽  
Interesting Candidate ◽  
Centrifugal Distortion Constants

Context. Thioformamide NH2CHS is a sulfur-bearing analog of formamide NH2CHO. The latter was detected in the interstellar medium back in the 1970s. Most of the sulfur-containing molecules detected in the interstellar medium are analogs of corresponding oxygen-containing compounds. Therefore, thioformamide is an interesting candidate for a search in the interstellar medium. Aims. A previous study of the rotational spectrum of thioformamide was limited to frequencies below 70 GHz and to transitions with J ≤ 3. The aim of this study is to provide accurate spectroscopic parameters and rotational transition frequencies for thioformamide to enable astronomical searches for this molecule using radio telescope arrays at millimeter wavelengths. Methods. The rotational spectrum of thioformamide was measured and analyzed in the frequency range 150−660 GHz using the Lille spectrometer. We searched for thioformamide toward the high-mass star-forming region Sagittarius (Sgr) B2(N) using the ReMoCA spectral line survey carried out with the Atacama Large Millimeter/submillimeter Array. Results. Accurate rigid rotor and centrifugal distortion constants were obtained from the analysis of the ground state of parent, 34S, 13C, and 15N singly substituted isotopic species of thioformamide. In addition, for the parent isotopolog, the lowest two excited vibrational states, v12 = 1 and v9 = 1, were analyzed using a model that takes Coriolis coupling into account. Thioformamide was not detected toward the hot cores Sgr B2(N1S) and Sgr B2(N2). The sensitive upper limits indicate that thioformamide is nearly three orders of magnitude at least less abundant than formamide. This is markedly different from methanethiol, which is only about two orders of magnitude less abundant than methanol in both sources. Conclusions. The different behavior shown by methanethiol versus thioformamide may be caused by the preferential formation of the latter (on grains) at late times and low temperatures, when CS abundances are depressed. This reduces the thioformamide-to-formamide ratio, because the HCS radical is not as readily available under these conditions.

scholarly journals Laboratory rotational spectrum and astronomical search for methoxyacetaldehyde

2018 ◽  
Vol 619 ◽  
pp. A67 ◽  
Author(s):  
L. Kolesniková ◽  
I. Peña ◽  
E. R. Alonso ◽  
B. Tercero ◽  
J. Cernicharo ◽  
...  
Keyword(s):  
Millimeter Wave ◽  
Ethyl Formate ◽  
High Mass ◽  
Spectroscopic Constants ◽  
Mass Star ◽  
Rotational Spectrum ◽  
Stable Conformer ◽  
Dark Cloud ◽  
Star Forming ◽  
Star Forming Regions

Context. Methoxyacetaldehyde belongs to a group of structural isomers with the general formula C3H6O2, 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.Methods. The rotational spectrum of methoxyacetaldehyde was recorded at room-temperature from 75 to 120 GHz and from 170 to 310 GHz using the millimeter-wave spectrometer in Valladolid. Additional measurements were also performed at conditions of supersonic expansion from 6 to 18 GHz. The assigned rotational transitions were analyzed using theS-reduced semirigid-rotor Hamiltonian.Results. We newly assigned over 1000 lines for the most stable conformer of methoxyacetaldehyde in its ground state and five lowest excited vibrational states, and precise sets of spectroscopic constants were obtained. We searched for spectral features of methoxyacetaldehyde in the high-mass star-forming regions Orion KL and Sagittarius B2, as well as in the cold dark cloud Barnard 1 (B1-b). No lines belonging to methoxyacetaldehyde were detected above the detection limit of our data. We provide upper limits to the methoxyacetaldehyde colum density in these sources.

scholarly journals Laboratory measurements and astronomical search for cyanomethanimine

2018 ◽  
Vol 609 ◽  
pp. A121 ◽  
Author(s):  
M. Melosso ◽  
A. Melli ◽  
C. Puzzarini ◽  
C. Codella ◽  
L. Spada ◽  
...  
Keyword(s):  
High Sensitivity ◽  
Rotational Spectrum ◽  
Laboratory Measurements ◽  
Spectral Window ◽  
Star Forming ◽  
Star Forming Regions ◽  
Upper Limits ◽  
Stringent Constraint ◽  
Prebiotic Molecule ◽  
Radio Wavelength

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. Methods. High-resolution laboratory measurements of the rotational spectrum of C-cyanomethanimine were carried out in the 100–420 GHz range using a frequency-modulation absorption spectrometer. We then searched for the C-cyanomethanimine spectral features in the mm-wave range using the high-sensitivity and unbiased spectral surveys obtained with the IRAM 30-m antenna in the ASAI context, the earliest stages of star formation from starless to evolved Class I objects being sampled. Results. For both the Z and E isomers, the spectroscopic work has led to an improved and extended knowledge of the spectroscopic parameters, thus providing accurate predictions of the rotational signatures up to ~700 GHz. So far, no C-cyanomethanimine emission has been detected toward the ASAI targets, and upper limits of the column density of ~1011–1012 cm-2 could only be derived. Consequently, the C-cyanomethanimine abundances have to be less than a few 10-10 for starless and hot-corinos. A less stringent constraint, ≤10-9, is obtained for shocks sites. Conclusions. The combination of the upper limits of the abundances of C-cyanomethanimine together with accurate laboratory frequencies up to ~700 GHz poses the basis for future higher sensitivity searches around Sun-like-star forming regions. For compact (typically less than 1″) and chemically enriched sources such as hot-corinos, the use of interferometers as NOEMA and ALMA in their extended configurations are clearly needed.

scholarly journals Constraining photoionization models with a reprojected optical diagnostic diagram

2020 ◽  
Vol 499 (4) ◽  
pp. 5749-5764 ◽  
Author(s):  
Xihan Ji ◽  
Renbin Yan
Keyword(s):  
Star Formation ◽  
Active Galactic Nuclei ◽  
Galactic Nuclei ◽  
Theoretical Models ◽  
Line Ratio ◽  
Star Forming ◽  
Optical Diagnostic ◽  
Diagnostic Diagram ◽  
Upper Limits ◽  
Nitrogen Abundance

ABSTRACT Optical diagnostic diagrams are powerful tools to separate different ionizing sources in galaxies. However, the model-constraining power of the most widely used diagrams is very limited and challenging to visualize. In addition, there have always been classification inconsistencies between diagrams based on different line ratios, and ambiguities between regions purely ionized by active galactic nuclei (AGNs) and composite regions. We present a simple reprojection of the 3D line ratio space composed of [N ii]λ6583/H α, [S ii]λλ6716, 6731/H α, and [O iii]λ5007/H β, which reveals its model-constraining power and removes the ambiguity for the true composite objects. It highlights the discrepancy between many theoretical models and the data loci. With this reprojection, we can put strong constraints on the photoionization models and the secondary nitrogen abundance prescription. We find that a single nitrogen prescription cannot fit both the star-forming locus and AGN locus simultaneously, with the latter requiring higher N/O ratios. The true composite regions stand separately from both models. We can compute the fractional AGN contributions for the composite regions, and define demarcations with specific upper limits on contamination from AGN or star formation. When the discrepancy about nitrogen prescriptions gets resolved in the future, it would also be possible to make robust metallicity measurements for composite regions and AGNs.

scholarly journals The prospects for observing [O iii] 52 micron emission from galaxies during the Epoch of Reionization

2021 ◽  
Vol 504 (1) ◽  
pp. 723-730
Author(s):  
Shengqi Yang ◽  
Adam Lidz ◽  
Gergö Popping
Keyword(s):  
Fine Structure ◽  
Interstellar Medium ◽  
Emission Line ◽  
Parameter Space ◽  
Gas Density ◽  
Star Forming ◽  
Upper Limits ◽  
Redshift Galaxies

ABSTRACT The [O iii] 88 $\mu$m fine-structure emission line has been detected into the Epoch of Reionization (EoR) from star-forming galaxies at redshifts 6 < z ≲ 9 with ALMA. These measurements provide valuable information regarding the properties of the interstellar medium (ISM) in the highest redshift galaxies discovered thus far. The [O iii] 88 $\mu$m line observations leave, however, a degeneracy between the gas density and metallicity in these systems. Here, we quantify the prospects for breaking this degeneracy using future ALMA observations of the [O iii] 52 $\mu$m line. Among the current set of 10 [O iii] 88 $\mu$m emitters at 6 < z ≲ 9, we forecast 52 $\mu$m detections (at 6σ) in SXDF-NB1006-2, B14-6566, J0217-0208, and J1211-0118 within on-source observing times of 2–10 h, provided their gas densities are larger than about nH ≳ 102–103 cm−3. Other targets generally require much longer integration times for a 6σ detection. Either successful detections of the 52 $\mu$m line or reliable upper limits will lead to significantly tighter constraints on ISM parameters. The forecasted improvements are as large as ∼3 dex in gas density and ∼1 dex in metallicity for some regions of parameter space. We suggest SXDF-NB1006-2 as a promising first target for 52 $\mu$m line measurements. We discuss how such measurements will help in understanding the mass–metallicity relationship during the EoR.

scholarly journals Observational constraints on the multiphase nature of outflows using large spectroscopic surveys at z ∼ 0

2020 ◽  
Vol 494 (3) ◽  
pp. 4266-4278 ◽  
Author(s):  
G W Roberts-Borsani
Keyword(s):  
Total Mass ◽  
High Mass ◽  
Ionized Gas ◽  
Star Forming ◽  
Gas Phases ◽  
Normal Galaxies ◽  
Upper Limits ◽  
Outflow Rate ◽  
Mass Outflow ◽  
Atomic Gas

ABSTRACT Mass outflow rates and loading factors are typically used to infer the quenching potential of galactic-scale outflows. However, these generally rely on observations of a single gas phase that can severely underestimate the total ejected gas mass. To address this, we use observations of high mass (≥1010 M⊙), normal star-forming galaxies at z ∼ 0 from the MaNGA, xCOLD GASS, xGASS, and ALFALFA surveys and a stacking of Na d, Hα, CO(1–0), and H i 21 cm tracers with the aim of placing constraints on an average, total mass outflow rate, and loading factor. We find detections of outflows in both neutral and ionized gas tracers, with no detections in stacks of molecular or atomic gas emission. Modelling of the outflow components reveals velocities of |vNa d| = 131 km s−1 and |vHα| = 439 km s−1 and outflow rates of $\dot{M}_{\rm {Na\,\small{D}}}$ = 7.55 M⊙ yr−1 and $\dot{M}_{\text{H}\alpha }$ = 0.10 M⊙ yr−1 for neutral and ionized gas, respectively. Assuming a molecular/atomic outflow velocity of 200 km s−1, we derive upper limits of $\dot{M}_{\text{CO}}\lt 19.43$ M⊙ yr−1 and $\dot{M}_{\rm {H\,\small {I}}}\lt $ 26.72 M⊙ yr−1 for the molecular and atomic gas, respectively. Combining the detections and upper limits, we find average total outflow rates of $\dot{M}_{\text{tot}}\lesssim$27 M⊙ yr−1 and a loading factor of ηtot ≲ 6.39, with molecular gas likely contributing ≲72 per cent of the total mass outflow rate, and neutral and ionized gas contributing ∼28 and <1 per cent, respectively. Our results suggest that, to first order, a degree of quenching via ejective feedback could occur in normal galaxies when considering all gas phases, even in the absence of an active galactic nucleus.

Spectroscopic investigations of hydrogen bonding interactions in the gas phase. II. The determination of the geometry and potential constants of the hydrogen-bonded heterodimer CH 3 CN • • • HF from its microwave rotational spectrum

1980 ◽  
Vol 370 (1741) ◽  
pp. 239-255 ◽  
Keyword(s):  
Hydrogen Bonding ◽  
Gas Phase ◽  
Spectroscopic Constants ◽  
Rotational Spectrum ◽  
Hydrogen Bonding Interactions ◽  
Isotopic Species ◽  
Microwave Rotational Spectrum ◽  
Vibration Rotation ◽  
Hydrogen Bonded

The microwave rotational spectrum of the hydrogen-bonded heterodimer CH 3 CN • • • HF has been identified and shown to be characteristic of a symmetric top. A detailed analysis of several rotational transitions for a variety of isotopic species gives the spectroscopic constants summarized in the following table: Rotational constants/MHz, vibration-rotation constants/MHz and vibrational separations/cm -1 of CH 3 CN • • • HF

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