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Dorschner, Stephan

doi:10.3936/35

Cited by 4 publications

(6 citation statements)

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“…For the opacities of the dust we use a mixture of silicates (∼58%), iron sulphide (∼18%), and carbonaceous dust grains (∼24%) with an average density of ρmix = 3.2 g/cm 3 (Min et al 2011) and a porosity of p = 0.625, corresponding to the density ρ = 1.2 g/cm 3 used in the dust evolution simulations. The indices of refraction are obtained from: Dorschner et al (1995); Henning & Stognienko (1996) for the silicates, Begemann et al (1994) for the iron sulphide, and Preibisch et al (1993) for the carbonaceous dust grains. For Figure A1.…”

Section: A2 Radiative Transfer and Synthetic Observationsmentioning

confidence: 99%

Constraining turbulence mixing strength in transitional discs with planets using SPHERE and ALMA

Ovelar¹,

Pinilla²,

Min³

et al. 2016

Monthly Notices of the Royal Astronomical Society: Letters

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We investigate the effect that the turbulent mixing strength parameter α turb plays on near-infrared polarimetric and sub-millimetre interferometric imaging observations of transitional discs with a gap carved by a planet. We generate synthetic observations of these objects with ALMA and VLT/SPHERE-ZIMPOL by combining hydrodynamical, dust evolution, radiative transfer and instrument models for values of α turb = [10 −4 , 10 −3 , 10 −2 ]. We find that, through a combination of effects on the viscosity of the gas, the turbulent mixing and dust evolution processes, α turb strongly affects the morphology of the dust distribution that can be traced with these observations. We constrain the value of α turb to be within an order of magnitude of 10 −3 in TD sources that show cavities in sub-mm continuum images while featuring continuous distribution of dust or smaller cavities in NIR-polarimetric images.

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Section: A2 Radiative Transfer and Synthetic Observationsmentioning

confidence: 99%

Constraining turbulence mixing strength in transitional discs with planets using SPHERE and ALMA

Ovelar¹,

Pinilla²,

Min³

et al. 2016

Monthly Notices of the Royal Astronomical Society: Letters

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“…Alternatively, the difference between the average IRS spectrum of quasars and the IRS spectra of our three galaxies could be due to different silicate composition. Dorschner et al (1995) have experimentally demonstrated that the absorption in the UV, optical and near-IR up to λ < 8 µm of amorphous silicate dust decreases with the decrease of the iron content in the dust. As shown in Figure 4 of Dorschner et al (1995), the imaginary part of the index of refraction of MgSiO 3 is smaller than that of Mg 0.4 Fe 0.6 SiO 3 by a factor of > 10.…”

Section: Discussionmentioning

confidence: 99%

“…Dorschner et al (1995) have experimentally demonstrated that the absorption in the UV, optical and near-IR up to λ < 8 µm of amorphous silicate dust decreases with the decrease of the iron content in the dust. As shown in Figure 4 of Dorschner et al (1995), the imaginary part of the index of refraction of MgSiO 3 is smaller than that of Mg 0.4 Fe 0.6 SiO 3 by a factor of > 10. It is possible that the silicate dust in quasars and typical AGNs are iron-rich, while the silicate dust in the three galaxies are iron-poor.…”

Section: Discussionmentioning

confidence: 99%

“…It is possible that the silicate dust in quasars and typical AGNs are iron-rich, while the silicate dust in the three galaxies are iron-poor. In Figure 3b we show the mass absorption coefficients calculated for three amorphous pyroxene dust species: MgSiO 3 , Mg 0.7 Fe 0.3 SiO 3 , and Mg 0.4 Fe 0.6 SiO 3 , with the refractive indices taken from Dorschner et al (1995). All dust species are assumed to be spherical and have a radius of a = 0.1 µm.…”

Section: Discussionmentioning

confidence: 99%

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A Tale of Three Galaxies: Anomalous Dust Properties in Iras F10398+1455, Iras F21013–0739, and SDSS J0808+3948

Xie¹,

Hao²,

Li³

2014

ApJ

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On a galactic scale the 9.7 µm silicate emission is usually only seen in type 1 active galactic nuclei (AGNs). They usually also display a flat emission continuum at ∼5-8 µm and the absence of polycyclic aromatic hydrocarbon (PAH) emission bands. In contrast, starburst galaxies, luminous infrared (IR) galaxies (LIRGs), and ultraluminous IR galaxies (ULIRGs) exhibit a red 5-8 µm emission continuum, strong 9.7 µm and 18 µm silicate absorption features, and strong PAH emission bands. Here we report the detection of anomalous dust properties by Spitzer/Infrared Spectrograph in three galaxies (IRAS F10398+1455, IRAS F21013-0739 and SDSS J0808+3948) which are characterized by the simultaneous detection of a red 5-8 µm emission continuum, the 9.7 and 18 µm silicate emission features as well as strong PAH emission bands. These apparently contradictory dust IR emission properties are discussed in terms of iron-poor silicate composition, carbon dust deficit, small grain size and low dust temperature in the young AGN phase of these three galaxies.

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“…The ubiquitous and conspicuous 10 and 20-µm features are essential to this choice (see, for instance, the study of forsterite (Olivine group) and enstatite ( Pyroxene group) by Pegourie and Papoular 1985). In the visible, these silicates were found to be fairly transparent (see Nitsan et al 1978, Palik 1985Dorschner et al 1995). This was difficult to reconcile with observations of polarization of InterStellar (IS) visible light which exhibits a wide, prominent, asymmetric bump whose peak wavelength, λmax, varies from 0.3 to 0.8 µm, with a mean value of 0.55 (see Spitzer 1978;Whittet 2003, Fig.…”

Section: Introductionmentioning

confidence: 99%

A new interpretation of Serkowski’s polarization law

Papoular

2018

Monthly Notices of the Royal Astronomical Society

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The basic tenets of the alternative interpretation to be presented here are that the spectral profiles of the star light polarization peaks observed in the visible and near IR are a result of the optical properties of silicate grains in the same spectral range, not of the grain size, provided it remains within the range of Rayleigh's approximation. The silicate properties are those obtained experimentally by Scott and Duley (1996) for the non-iron bearing amorphous forsterite and enstatite. The whole range of observed Serkowski polarization profiles can be simulated with mixtures made of forsterite plus an increasing fraction (0 to 0.5) of enstatite as the spectral peak shifts from 0.8 to 0.3 µm. Fits to individual observed polarization spectra are also demonstrated.The optical extinction of silicates in the vis/IR (the "transparency range") can be understood by analogy with the thoroughly studied amorphous hydrogenated carbons and amorphous silica. It is due to structural disorder (dangling bonds and coordination defects) and impurities, which give rise to electronic states in the forbidden gap of semiconductors. Because they are partially localized, their extinction power is dramatically reduced and has been ignored or simply described by a low, flat plateau. As their number density depends on the environment, one expects variations in the ratio of optical extinction coefficients in the visible and mid-IR.It is also argued that the measured steep rise of extinction beyond 3 µm −1 into the UV is due to atomic transitions, and so cannot give rise to coherent molecular polarization, but only localized extinction.

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Cited by 4 publications

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Constraining turbulence mixing strength in transitional discs with planets using SPHERE and ALMA

Constraining turbulence mixing strength in transitional discs with planets using SPHERE and ALMA

A Tale of Three Galaxies: Anomalous Dust Properties in Iras F10398+1455, Iras F21013–0739, and SDSS J0808+3948

A new interpretation of Serkowski’s polarization law

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