Emission and extinction of ground and vapor-condensed silicates from 4 to 14 microns and the 10 micron silicate feature

Stephens, John; Rusell, R. W.

doi:10.1086/156904

Cited by 64 publications

(22 citation statements)

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“…In addition, we assume that the VSGs have sizes up to 20 nm, compared to 15 nm as in the Galaxy. This latter assumption does not necessarily change the physical properties of the VSGs, like surface-to-volume ratio and heat capacity (Kamijo et al 1975;Stephens & Russell 1979).…”

Section: Very Small Grainsmentioning

confidence: 99%

Cold dust in a selected sample of nearby galaxies

Dumke

Krause

Wielebinski

2004

A&A

115

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Abstract.We have observed the continuum emission of the interacting galaxy NGC 4631 at λλ 870 µm and 1.23 mm using the Heinrich-Hertz-Telescope on Mt. Graham and the IRAM 30-m telescope on Pico Veleta. We have obtained fully sampled maps which cover the optical emission out to a radius of about 7 at both wavelengths. For a detailed analysis, we carefully subtracted the line contributions and synchrotron and free-free emission from the data, which added up to 6% at 1.23 mm and 10% at 0.87 mm. We combined the flux densities with FIR data to obtain dust spectra and calculate dust temperatures, absorption cross sections, and masses. Assuming a "standard" dust model, which consists of two populations of big grains at moderate and warm temperatures, we obtained temperatures of 18 K and 50 K for the both components. However, such a model suffers from an excess of the radiation at λ 1.23 mm, and the dust absorption cross section seems to be enhanced by a factor 3 compared to previous results and theoretical expectations. At large galactocentric radii, where the galaxy shows disturbances as a result of gravitational interaction, this effect seems to be even stronger. Some possibilities to resolve these problems are discussed. The data could be explained by a very cold dust component at a temperature of 4-6 K, an increased abundance of very small grains, or a component of grains with unusual optical properties. We favour the latter possibility, since the first two lead to inconsistencies

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Section: Very Small Grainsmentioning

confidence: 99%

Cold dust in a selected sample of nearby galaxies

Dumke

Krause

Wielebinski

2004

A&A

115

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“…The 1 1.2 p m peak and 11.9 p m shoulder have been confidently attributed to crystalline olivine (Campins and Ryan, 1989;Hanner et al, 1994a), whereas amorphous or glassy olivine is thought to explain the 10.0 p m feature. With less confidence, crystalline pyroxene probably explains the 10.5 p m feature and amorphous pyroxene the 9.32 p m feature (Stephen and Russell, 1979). Bands at -3.4 p m have been attributed to C-H stretch.…”

Section: The Nature Of Cometsmentioning

confidence: 99%

Laboratory simulation of the physical processes occurring on and near the surfaces of comet nuclei

Sears

Kochan

Huebner

1999

Meteorit & Planetary Scien

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Abstract-Laboratory comet simulation experiments are discussed in the context of theoretical models and recent ground-based and spacecraft observations, especially the Giotto observations of Pmalley. The set-up of various comet simulation experiments is reviewed. A number of small-scale experiments have been performed in many laboratories since the early 1960s. However, the largest and most ambitious series of experiments were the comet simulation experiments known as KOSI (German = Kometen Simulation). These experiments were prompted by the appearance of Comet PMalley in 1986 and in planning for the European Space Agency's Rossetta mission that was originally scheduled to return samples. They were performed between 1987 and 1993 using the German Space Agency's (DLR) space hardware testing facilities in Cologne. As with attempts to reproduce any natural phenomenon in the laboratory, there are deficiencies in such experiments while there are major new insights to be gained. Simulation experiments have enabled the development of methods for making comet analogues and for exploring the properties of such materials in detail. These experiments have provided new insights into the morphology and physical behavior of aggregates formed from silicate grains likely to exist in comets. Formation of a dust mantle on the surfaces and a system of ice layers below the mantle caused by chemical differentiation have been identified after the insolation of the artificial comet. The mechanisms for heat transfer between the comet's surface and its interior, the associated gas diffusion from the interior of the surface, and compositional, structural, and isotopic changes that occur near the surface have been described by modeling the experimental results. The mechanisms of the ejection of dust and ice grains from the surface and the importance of gas-drag in propelling grains have also been explored.Where the telescope ends,

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“…Additional features in the interstellar extinction curve appear near 9.7 and 18 lm, indicating the presence of silicate grains (Knacke et al 1969;McCarthy et al 1980). Because both 9.7 and 18 lm features are broad bands, interstellar silicates have been suggested to be amorphous rather than crystalline (Day 1974;Stephens & Russell 1979). The presence of organic refractory components in interstellar grains has been manifested by the observations of near-infrared absorption bands (Sandford et al 1991).…”

Section: Introductionmentioning

confidence: 99%

Composition, Structure, and Size Distribution of Dust in the Local Interstellar Cloud

Kimura

Mann

Jeßberger

2003

ApJ

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The average properties of interstellar dust have previously been inferred from remote astronomical observations of interstellar extinction and from gas depletion measurements. In addition to recent high-resolution observations of gas absorption spectra, in situ measurements of dust in the solar system provide an alternative approach to deducing the properties of interstellar dust, in particular, those of dust in the Local Interstellar Cloud (LIC), in which the Sun resides. We constrain the composition and structure of dust in the LIC by the dust-phase elemental abundances derived from gas absorption measurements and by the dynamical behavior inferred from dust impact measurements. The elemental abundances of the LIC dust are consistent with coremantle grains consisting of Mg-rich pyroxene and Mg-rich olivine with inclusions of troilite, Fe-rich kamacite, and corundum in the core and organic refractory compounds of C, N, and O in the mantle. The mass of the organic refractory mantle is comparable to the mass of the silicate core that is abundant in pyroxene compared to olivine. Taking into account these results, the dynamical behavior of the LIC dust in the solar system indicates that bare silicates and bare carbonaceous materials may be present as grains smaller than 10 À17 kg. The LIC grains with mass exceeding 10 À17 kg are most likely aggregates of submicron-sized silicate core, organic mantle grains. The mass distribution of dust in the LIC can be well explained by coagulation growth of core-mantle grains but is scarcely explained by severe destruction of grains in interstellar shocks.

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Emission and extinction of ground and vapor-condensed silicates from 4 to 14 microns and the 10 micron silicate feature

Cited by 64 publications

References 0 publications

Cold dust in a selected sample of nearby galaxies

Cold dust in a selected sample of nearby galaxies

Laboratory simulation of the physical processes occurring on and near the surfaces of comet nuclei

Composition, Structure, and Size Distribution of Dust in the Local Interstellar Cloud

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