Do we really know the dust Systematics and uncertainties of the mid-infrared spectral analysis methods - Astrophysics > Earth and Planetary AstrophysicsReport as inadecuate




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Abstract: The spectral region around 10 micrometer, showing prominent dust emissionbands, is commonly used to derive the chemical composition of protoplanetarydust. Different analysis methods have been proposed for this purpose, but sofar, no comparative test has been performed to test their validity. Wecalculated model spectra of disk models with different geometries and centralsources, using a 2D radiative transfer code. These spectra were then fitted ina blind test using four different spectral decomposition methods. We studiedthe effect of disk structure flared vs. flat, inclination angle, size of theinner disk hole and stellar luminosity on the fitted chemical composition. Ourresults show that the derived dust compositions by all methods deviatesystematically from the real chemical composition. Out of the four testedspectral decomposition methods, our new two-layer temperature distributionmethod, differs the least from the input dust composition and the results showthe weakest systematic effects. The reason for the deviations of the resultsgiven by other methods lies in their simplifying assumptions e.g. singleaverage grain temperature or one component continuum. We also tested theinfluence of different noise levels on the results of the spectraldecomposition methods. We find that, for ground-based observations 8-13micrometer the expected uncertainty in the value of the crystallinity is about11% for a signal-to-noise ratio of 100, while for space-based observations7-17 micrometer the uncertainty is about 5%. On the basis of our results, wepropose a recipe for the analysis and interpretation of dust spectroscopy datain the mid-infrared which should be especially valuable for analysing Spitzerdata and ground-based infrared spectroscopy data in the 10 micrometer window.



Author: Attila Juhasz, Thomas Henning, Jeroen Bouwman, Cornelis Dullemond, Ilaria Pascucci, Daniel Apai

Source: https://arxiv.org/







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