Gas phase Elemental abundances in Molecular cloudS (GEMS). V. Methanol in Taurus

We present ground-based measurements of 126 nearby galaxy centers in 12CO and 92 in 13CO in various low-J transitions. More than 60 galaxies were measured in at least four lines. The average relative intensities of the first four J 12CO transitions are 1.00:0.92:0.70:0.57. In the first three J transitions, the average 12CO-to-13CO intensity ratios are 13.0, 11.6, and 12.8, with individual values in any transition ranging from 5 to 25. The sizes of central CO concentrations are well defined in maps, but poorly determined by multi-aperture photometry. On average, the J = 1−0 12CO fluxes increase linearly with the size of the observing beam. CO emission covers only a quarter of the HI galaxy disks. Using radiative transfer models (RADEX), we derived model gas parameters. The assumed carbon elemental abundances and carbon gas depletion onto dust are the main causes of uncertainty. The new CO data and published [CI] and [CII] data imply that CO, C°, and C+ each represent about one-third of the gas-phase carbon in the molecular interstellar medium. The mean beam-averaged molecular hydrogen column density is N(H2) = (1.5 ± 0.2)×1021 cm−2. Galaxy center CO-to-H2 conversion factors are typically ten times lower than the “standard” Milky Way X° disk value, with a mean X(CO) = (1.9 ± 0.2)×1019 cm−2/K km s−1 and a dispersion 1.7. The corresponding [CI]-H2 factor is five times higher than X(CO), with X[CI] = (9 ± 2)×1019 cm−2/K km s−1. No unique conversion factor can be determined for [CII]. The low molecular gas content of galaxy centers relative to their CO intensities is explained in roughly equal parts by high central gas-phase carbon abundances, elevated gas temperatures, and large gas velocity dispersions relative to the corresponding values in galaxy disks.

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Enhanced UV radiation and dense clumps in the molecular outflow of Mrk 231

Astronomy and Astrophysics ◽

10.1051/0004-6361/201936800 ◽

2020 ◽

Vol 633 ◽

pp. A163 ◽

Cited By ~ 2

Author(s):

Claudia Cicone ◽

Roberto Maiolino ◽

Susanne Aalto ◽

Sebastien Muller ◽

Chiara Feruglio

Keyword(s):

Gas Phase ◽

Uv Radiation ◽

Molecular Clouds ◽

Line Emission ◽

Molecular Gas ◽

Spectral Features ◽

Giant Molecular Clouds ◽

Dense Phase ◽

Molecular Outflow ◽

First Time

We present interferometric observations of the CN(1–0) line emission in Mrk 231 and combine them with previous observations of CO and other H2 gas tracers to study the physical properties of the massive molecular outflow. We find a strong boost of the CN/CO(1–0) line luminosity ratio in the outflow of Mrk 231, which is unprecedented compared to any other known Galactic or extragalactic astronomical source. For the dense gas phase in the outflow traced by the HCN and CN emissions, we infer XCN ≡ [CN]/[H2]> XHCN by at least a factor of three, with H2 gas densities of nH2 ∼ 105−6 cm−3. In addition, we resolve for the first time narrow spectral features in the HCN(1–0) and HCO+(1–0) high-velocity line wings tracing the dense phase of the outflow. The velocity dispersions of these spectral features, σv ∼ 7−20 km s−1, are consistent with those of massive extragalactic giant molecular clouds detected in nearby starburst nuclei. The H2 gas masses inferred from the HCN data are quite high, Mmol ∼ 0.3−5 × 108 M⊙. Our results suggest that massive complexes of denser molecular gas survive embedded into the more diffuse H2 phase of the outflow, and that the chemistry of these outflowing dense clouds is strongly affected by UV radiation.

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Aldehydes and sugars from evolved precometary ice analogs: Importance of ices in astrochemical and prebiotic evolution

Proceedings of the National Academy of Sciences ◽

10.1073/pnas.1418602112 ◽

2015 ◽

Vol 112 (4) ◽

pp. 965-970 ◽

Cited By ~ 76

Author(s):

Pierre de Marcellus ◽

Cornelia Meinert ◽

Iuliia Myrgorodska ◽

Laurent Nahon ◽

Thomas Buhse ◽

...

Keyword(s):

Gas Phase ◽

Molecular Clouds ◽

Room Temperature ◽

Laboratory Experiments ◽

Organic Residue ◽

Organic Residues ◽

Flight Mass Spectrometry ◽

The Earth ◽

Planetary Environment ◽

Complex Organic

Evolved interstellar ices observed in dense protostellar molecular clouds may arguably be considered as part of precometary materials that will later fall on primitive telluric planets, bringing a wealth of complex organic compounds. In our laboratory, experiments reproducing the photo/thermochemical evolution of these ices are routinely performed. Following previous amino acid identifications in the resulting room temperature organic residues, we have searched for a different family of molecules of potential prebiotic interest. Using multidimensional gas chromatography coupled to time-of-flight mass spectrometry, we have detected 10 aldehydes, including the sugar-related glycolaldehyde and glyceraldehyde—two species considered as key prebiotic intermediates in the first steps toward the synthesis of ribonucleotides in a planetary environment. The presence of ammonia in water and methanol ice mixtures appears essential for the recovery of these aldehydes in the refractory organic residue at room temperature, although these products are free of nitrogen. We finally point out the importance of detecting aldehydes and sugars in extraterrestrial environments, in the gas phase of hot molecular clouds, and, more importantly, in comets and in primitive meteorites that have most probably seeded the Earth with organic material as early as 4.2 billion years ago.

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The 6.4 keV Fe Line and the SiO Emission in the GC

Symposium - International Astronomical Union ◽

10.1017/s0074180900220354 ◽

2001 ◽

Vol 205 ◽

pp. 36-37

Author(s):

J. Martín-Pintado ◽

P. de Vicente ◽

N. Rodríguez-Fernández ◽

A. Fuente ◽

P. Planesas

Keyword(s):

Spatial Distribution ◽

Gas Phase ◽

Molecular Clouds ◽

Galactic Center ◽

X Rays ◽

Refractory Elements

We present a map of the Galactic center in the J=l-0 line of SiO covering the region mapped with the ASCA satellite in the 6.4 keV Fe line. We find a correlation between the spatial distribution of the Fe 6.4 keV line and the SiO emission. The SiO abundance increases by more than a factor of 20 in the regions with strong Fe 6.4 keV line. This indicates that the Fe 6.4 keV line mainly arises from molecular clouds with large gas phase abundance of refractory elements. We discuss the implications of the correlation on the origin of the hard X-rays, and the heating and the chemistry of the molecular clouds in the GC.

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Gas-phase synthetic pathways to benzene and benzonitrile: a combined microwave and thermochemical investigation

Physical Chemistry Chemical Physics ◽

10.1039/c8cp06070c ◽

2019 ◽

Vol 21 (6) ◽

pp. 2946-2956 ◽

Cited By ~ 9

Author(s):

Kin Long Kelvin Lee ◽

Brett A. McGuire ◽

Michael C. McCarthy

Keyword(s):

Low Temperature ◽

Gas Phase ◽

Molecular Clouds ◽

Theoretical Calculations ◽

Microwave Spectroscopy ◽

Temperature Conditions ◽

Thermochemical Investigation

Microwave spectroscopy and theoretical calculations show the formation of benzene – traced by benzonitrile – is efficient at low temperature conditions relevant to cold molecular clouds such as TMC-1.

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Forming NCO–in Dense Molecular Clouds: Possible Gas-Phase Chemical Paths From Quantum Calculations

The Journal of Physical Chemistry A ◽

10.1021/acs.jpca.5b10472 ◽

2016 ◽

Vol 120 (27) ◽

pp. 4693-4701 ◽

Cited By ~ 1

Author(s):

E. Yurtsever ◽

F. A. Gianturco ◽

R. Wester

Keyword(s):

Gas Phase ◽

Molecular Clouds ◽

Quantum Calculations ◽

Phase Chemical

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Interstellar Extinction and Elemental Abundances: Individual Sight Lines

The Astrophysical Journal Supplement Series ◽

10.3847/1538-4365/ac2cc3 ◽

2021 ◽

Vol 257 (2) ◽

pp. 63

Author(s):

Wenbo Zuo ◽

Aigen Li ◽

Gang Zhao

Keyword(s):

Gas Phase ◽

Interstellar Extinction ◽

Elemental Abundance ◽

Extinction Curve ◽

Galactic Chemical Evolution ◽

Space Telescopes ◽

Dust Extinction ◽

Elemental Abundances ◽

Hydrogen Column Density ◽

The Relationship

Abstract While it is well recognized that both the Galactic interstellar extinction curves and the gas-phase abundances of dust-forming elements exhibit considerable variations from one sight line to another, as yet most of the dust extinction modeling efforts have been directed to the Galactic average extinction curve, which is obtained by averaging over many clouds of different gas and dust properties. Therefore, any details concerning the relationship between the dust properties and the interstellar environments are lost. Here we utilize the wealth of extinction and elemental abundance data obtained by space telescopes and explore the dust properties of a large number of individual sight lines. We model the observed extinction curve of each sight line and derive the abundances of the major dust-forming elements (i.e., C, O, Si, Mg, and Fe) required to be tied up in dust (i.e., dust depletion). We then confront the derived dust depletions with the observed gas-phase abundances of these elements and investigate the environmental effects on the dust properties and elemental depletions. It is found that for the majority of the sight lines the interstellar oxygen atoms are fully accommodated by gas and dust and therefore there does not appear to be a “missing oxygen” problem. For those sight lines with an extinction-to-hydrogen column density A V /N H ≳ 4.8 × 10−22 mag cm2 H−1 there are shortages of C, Si, Mg, and Fe elements for making dust to account for the observed extinction, even if the interstellar C/H, Si/H, Mg/H, and Fe/H abundances are assumed to be protosolar abundances augmented by Galactic chemical evolution.

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Molecular depletions in cloud cores

Symposium - International Astronomical Union ◽

10.1017/s0074180900009347 ◽

1997 ◽

Vol 178 ◽

pp. 183-192 ◽

Cited By ~ 5

Author(s):

Lee G. Mundy ◽

Joseph P. McMullin

Keyword(s):

Gas Phase ◽

Chemical Evolution ◽

Quantitative Study ◽

Molecular Clouds ◽

Stellar Systems ◽

Gas Phase Molecules ◽

Cloud Cores

The condensation of gas-phase molecules onto grain surfaces in cold molecular clouds is widely expected, and the presence of the resultant icy mantles well established, but quantitative study of the gas-phase depletions has not proved easy. This paper reviews the methods for determining depletions and the associated problems. Further observations are critical to testing our expectations for depletions and for the chemical evolution of forming stellar systems.

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