scholarly journals Formation, Evolution and Destruction of Possible DIB Carriers: Dirty Molecular Hydrogen Ice Clusters

2013 ◽  
Vol 9 (S297) ◽  
pp. 381-382
Author(s):  
D. K. Lynch ◽  
L. S. Bernstein ◽  
F. O. Clark
Keyword(s):  
Interstellar Medium ◽  
Single Molecule ◽  
Molecular Hydrogen ◽  
Molecular Clouds ◽  
Single Layer ◽  
Molecular Clusters ◽  
Electronic Transitions ◽  
Giant Molecular Clouds ◽  
Diffuse Interstellar Bands ◽  
Optical Photons

AbstractWe suggest that the diffuse interstellar bands (DIBs) are absorption lines arising from electronic transitions in molecular clusters primarily composed of a single molecule, atom, or ion (“seed”), embedded in a single-layer shell of H2 molecules (Bernstein et al. 2013). We refer to these clusters as CHCs (Contaminated H2 Clusters). CHCs arise from cm-sized, dirty H2 ice balls, called CHIMPs (Contaminated H2 Ice Macro-Particles), formed in cold, dense, Giant Molecular Clouds (GMCs), and later released into the interstellar medium (ISM) upon GMC disruption. Absorption by the CHIMP of a UV photon releases CHCs. CHCs produce DIBs when they absorb optical photons. When this occurs, the absorbed photon energy disrupts the CHC.

scholarly journals Dirty H2 Molecular Clusters as the DIB Sources: Spectroscopic and Physical Properties

2013 ◽  
Vol 9 (S297) ◽  
pp. 378-380
Author(s):  
L. S. Bernstein ◽  
F. O. Clark ◽  
D. K. Lynch
Keyword(s):  
Single Molecule ◽  
Molecular Clouds ◽  
Rotational Temperature ◽  
Single Layer ◽  
Molecular Clusters ◽  
Microwave Emission ◽  
Giant Molecular Clouds ◽  
Induced Dipole ◽  
Spectral Profiles ◽  
Uv Photons

AbstractWe propose that the diffuse interstellar bands (DIBs) arise from absorption lines of electronic transitions in molecular clusters primarily composed of a single molecule, atom, or ion (“seed”), embedded in a single-layer shell of H2 molecules (Bernstein et al. 2013). Less abundant variants of the cluster, including two seed molecules and/or a two-layer shell of H2 molecules may also occur. The lines are broadened, blended, and wavelength-shifted by interactions between the seed and surrounding H2 shell. We refer to these clusters as CHCs (Contaminated H2 Clusters). CHC spectroscopy matches the diversity of observed DIB spectral profiles, and provides good fits to several DIB profiles based on a rotational temperature of 10 K. CHCs arise from ~cm-sized, dirty H2 ice balls, called CHIMPs (Contaminated H2 Ice Macro-Particles), formed in cold, dense, Giant Molecular Clouds (GMCs), and later released into the interstellar medium (ISM) upon GMC disruption. Attractive interactions, arising from Van der Waals and ion-induced dipole potentials, between the seeds and H2 molecules enable CHIMPs to attain cm-sized dimensions. When an ultraviolet (UV) photon is absorbed in the outer layer of a CHIMP, it heats the icy matrix and expels CHCs into the ISM. While CHCs are quickly destroyed by absorbing UV photons, they are replenished by the slowly eroding CHIMPs. Since CHCs require UV photons for their release, they are most abundant at, but not limited to, the edges of UV-opaque molecular clouds, consistent with the observed, preferred location of DIBs. An inherent property of CHCs, which can be characterized as nanometer size, spinning, dipolar dust grains, is that they emit in the radio-frequency region. Thus, CHCs offer a natural explanation to the anomalous microwave emission (AME) feature in the ~10-100 GHz spectral region.

scholarly journals Detection of buckminsterfullerene emission in the diffuse interstellar medium

2017 ◽  
Vol 605 ◽  
pp. L1 ◽  
Author(s):  
O. Berné ◽  
N. L. J. Cox ◽  
G. Mulas ◽  
C. Joblin
Keyword(s):  
Interstellar Medium ◽  
Charge State ◽  
Laboratory Data ◽  
Electronic Transitions ◽  
Hot Stars ◽  
Large Molecules ◽  
Diffuse Interstellar Bands ◽  
Classical Models ◽  
Vibrational Bands

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. C60+) 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 . According to classical models that compute the charge state of large molecules in space, C60 is expected to be mostly neutral in the diffuse ISM. This is in agreement with the abundances of diffuse C60 we derive here from observations.

scholarly journals Molecules and Dust in the Magellanic Clouds

1984 ◽  
Vol 108 ◽  
pp. 319-332
Author(s):  
F. P. Israel
Keyword(s):  
Interstellar Medium ◽  
Molecular Hydrogen ◽  
Molecular Clouds ◽  
Total Mass ◽  
Spiral Galaxies ◽  
Magellanic Clouds ◽  
Major Constituent ◽  
Early Type ◽  
Disk Mass ◽  
Early Type Stars

A variety of studies over the last decade has shown molecular hydrogen to be a major constituent of the interstellar medium both in our Galaxy and in other spiral galaxies (Morris and Rickard, 1982). Our Galaxy contains roughly M(H2) = 4 × 109 M⊙; between R = 2 kpc and R = 10 kpc the H2 mass is one to three times that of HI; at the solar circle about 12 per cent of the total disk mass is in the form of H2; most of this mass is in the form of several thousand giant molecular cloud complexes (GMCs) with sizes d > 20 pc and masses M(H2) > 105 MO (Cohen et al, 1980; Sanders, 1981; Dame, 1983). These GMCs mainly consist of clumps with much smaller scales of order a few pc or less (e.g. Bally and Israel, 1983). Apart from their contribution to the total mass of the galactic interstellar medium, molecular clouds are also important as they are the major birthsite of massive early-type stars (see the review by Habing and Israel, 1979).

scholarly journals Giant molecular clouds in the galaxy: distribution, mass, size and age

1979 ◽  
Vol 84 ◽  
pp. 35-52 ◽  
Author(s):  
P. M. Solomon ◽  
D. B. Sanders ◽  
N. Z. Scoville
Keyword(s):  
Interstellar Medium ◽  
Molecular Clouds ◽  
Galactic Disk ◽  
Free Fall ◽  
Major Constituent ◽  
Giant Molecular Clouds ◽  
Interstellar Clouds ◽  
Dominant Component ◽  
The Galaxy ◽  
Galactic Distribution

Millimeter wave observations of emission from the CO molecule have become, over the past eight years, the dominant method for determining the physical properties of dense interstellar clouds, composed primarily of molecular hydrogen and for exploring the structure and kinematics of the galactic disk. In this paper we briefly review the CO survey results in the literature (Section 2) and then present new results (Section 3-7) of an extensive 13CO and 12CO survey of the galactic distribution, size, mass and age of molecular clouds. The interpretation of this survey leads to a new picture of the interstellar medium dominated by very massive stable long-lived clouds which we refer to as Giant Molecular Clouds. We find that Giant Molecular Clouds (GMC's) with M = 105–3 × 106M⊙ are a major constituent of the galactic disk, the dominant component of the interstellar medium in the galaxy interior to the sun and the most massive objects in the galaxy. We find that the interstellar medium and star formation are dominated by massive gravitationally bound clouds in which stars and associations are forming but at a very low rate in comparison to the free fall time. The galactic distribution of the molecules as traced by CO emission is interpreted as the distribution of GMC's. As the most massive objects in the galaxy they are also basic to the dynamics of the disk.

scholarly journals Galactic star formation in parsec-scale resolution simulations

2010 ◽  
Vol 6 (S270) ◽  
pp. 487-490
Author(s):  
Leila C. Powell ◽  
Frederic Bournaud ◽  
Damien Chapon ◽  
Julien Devriendt ◽  
Adrianne Slyz ◽  
...  
Keyword(s):  
Star Formation ◽  
High Resolution ◽  
Interstellar Medium ◽  
Molecular Clouds ◽  
Giant Molecular Clouds ◽  
Gas Distribution ◽  
Computational Problem ◽  
Cold Gas

AbstractThe interstellar medium (ISM) in galaxies is multiphase and cloudy, with stars forming in the very dense, cold gas found in Giant Molecular Clouds (GMCs). Simulating the evolution of an entire galaxy, however, is a computational problem which covers many orders of magnitude, so many simulations cannot reach densities high enough or temperatures low enough to resolve this multiphase nature. Therefore, the formation of GMCs is not captured and the resulting gas distribution is smooth, contrary to observations. We investigate how star formation (SF) proceeds in simulated galaxies when we obtain parsec-scale resolution and more successfully capture the multiphase ISM. Both major mergers and the accretion of cold gas via filaments are dominant contributors to a galaxy's total stellar budget and we examine SF at high resolution in both of these contexts.

scholarly journals Molecular Clouds Within 100 pc

1984 ◽  
Vol 81 ◽  
pp. 229-234
Author(s):  
Leo Blitz ◽  
Loris Magnani ◽  
Lee Mundy
Keyword(s):  
Interstellar Medium ◽  
Molecular Hydrogen ◽  
Molecular Clouds ◽  
Milky Way ◽  
Velocity Dispersion ◽  
Scale Height ◽  
Galactic Latitude ◽  
Local Interstellar Medium ◽  
High Galactic Latitude ◽  
The Mean

AbstractObservations at the 2.6 mm line of CO reveal the presence of a large number of molecular clouds at high galactic latitude. If the velocity dispersion of the clouds is a measure of their scale height, the mean distance of the ensemble we have detected is 100 pc. The clouds are unusual in that either they are not gravitationally bound or they are very deficient in CO relative to molecular hydrogen. These clouds represent a heretofore unrecognized component of the local interstellar medium. If they are pervasive in the Milky Way, they probably represent the small molecular cloud component of the interstellar medium.

scholarly journals The Distribution of Molecular Clouds in Spiral Galaxies

1983 ◽  
Vol 100 ◽  
pp. 35-42
Author(s):  
P. M. Solomon
Keyword(s):  
Millimeter Wave ◽  
Molecular Hydrogen ◽  
Surface Density ◽  
Molecular Clouds ◽  
Spiral Galaxies ◽  
Galactic Disk ◽  
Giant Molecular Clouds ◽  
The Galaxy ◽  
Co Emission ◽  
Half Thickness

The use of millimeter wave CO emission as a tracer of molecular hydrogen in the Galaxy (Scoville and Solomon 1975) showed that most of the H2 unlike HI is concentrated in the inner part of the Galaxy in a “ring” between 4–8 kpc and in the inner 1 kpc. Subsequent surveys (Gordon and Burton 1976, Cohen and Thaddeus 1977, Solomon etal. 1979) confirmed this picture with more extensive data. The molecular interstellar medium was shown to be dominated by Giant Molecular Clouds with individual masses between 105 and 3·106M⊙ (Solomon etal. 1979, Solomon and Sanders 1980). The GMC's confined to a layer with a half thickness of only 60 pc are an important component of the galactic disk, and the most massive objects in the galaxy. They affect the dynamics of the disk by contributing significantly to the surface density and through their individual gravitational interactions with stars.

Formation of Giant Molecular Clouds Associated with Spiral Structure

1991 ◽  
Vol 9 (2) ◽  
pp. 200-202 ◽  
Author(s):  
Guoxuan Song
Keyword(s):  
Numerical Simulation ◽  
Mass Spectrum ◽  
High Resolution ◽  
Numerical Integration ◽  
Molecular Hydrogen ◽  
Molecular Clouds ◽  
Spiral Galaxies ◽  
Spiral Structure ◽  
Giant Molecular Clouds ◽  
Co Emission

AbstractMolecular hydrogen in spiral galaxies is distributed in clumps, i.e., molecular clouds, which have mass between 103M⊙ and 106M⊙ and a mass spectrum of n(m) ∝ m−1.6. Molecular clouds with masses greater than 105M⊙, are called giant molecular clouds (GMCs). It is generally accepted that GMCs are formed by the coalescence of molecular clouds through their collision. This process is studied by both numerical simulation and numerical integration. The observation with high resolution identified a great number of CO emission cores in galaxies. Based on this result, the aggregation or clustering formation of GMCs is numerically simulated. In the process of either coalescence or clustering, spiral perturbation plays an important role.

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