BETTER ALTERNATIVES TO "ASTRONOMICAL SILICATE": LABORATORY-BASED OPTICAL FUNCTIONS OF CHONDRITIC/SOLAR ABUNDANCE GLASS WITH APPLICATION TO HD 161796

ABSTRACT "Astronomical" or "circumstellar" silicate optical functions (real and imaginary indices of refraction and ) have previously been derived from compositionally and structurally disparate samples; past values were compiled from different sources in the literature, and are...

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Bibliographic Details
Published in:The Astrophysical journal 2015-08, Vol.809 (1), p.1-12
Main Authors: Speck, A. K., Pitman, K. M., Hofmeister, A. M.
Format: Article
Language:English
Subjects:
Astronomical bodies
ASTROPHYSICS, COSMOLOGY AND ASTRONOMY
COMPARATIVE EVALUATIONS
COMPUTERIZED SIMULATION
COSMIC DUST
dust, extinction
Electronics
ELEMENT ABUNDANCE
ENERGY SPECTRA
Extrapolation
GLASS
infrared: ISM
INTERPOLATION
IRON
Mathematical models
methods: laboratory: solid state
RADIANT HEAT TRANSFER
REFRACTION
SILICATES
SOLIDS
STARS
ULTRAVIOLET RADIATION
ultraviolet: ISM
Wavelengths
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Summary:ABSTRACT "Astronomical" or "circumstellar" silicate optical functions (real and imaginary indices of refraction and ) have previously been derived from compositionally and structurally disparate samples; past values were compiled from different sources in the literature, and are essentially kluges of observational, laboratory, and extrapolated or interpolated values. These synthetic optical functions were created because astronomers lack the quantitative data on amorphous silicates at all wavelengths needed for radiative transfer modeling. This paper provides optical functions that (1) are created with a consistent methodology, (2) use the same sample across all wavelengths, and (3) minimize interpolation and extrapolation wherever possible. We present electronic data tables of optical functions derived from mid-ultraviolet to far-infrared (FIR) laboratory transmission spectra for two materials: iron-free glass with chondritic/solar atmospheric abundances, and metallic iron. We compare these optical functions to other popular n, k data used to model amorphous silicates (e.g., "astronomical" or "circumstellar" silicate), both directly and in application to a simple system: the dust shell of the post-AGB star HD 161796. Using the new optical functions, we find that the FIR profile of model spectral energy distributions are significantly affected by the ratio of glass to iron. Our case study on HD 161796 shows that in modeling with our new optical functions, the mineralogy is markedly different from that derived using synthetic optical functions and suggests a new scenario of crystalline silicate formation.
ISSN:0004-637X
1538-4357
1538-4357
DOI:10.1088/0004-637X/809/1/65