Grain growth across protoplanetary discs: 10-micron silicate feature versus millimetre slope - Astrophysics > Solar and Stellar AstrophysicsReportar como inadecuado




Grain growth across protoplanetary discs: 10-micron silicate feature versus millimetre slope - Astrophysics > Solar and Stellar Astrophysics - Descarga este documento en PDF. Documentación en PDF para descargar gratis. Disponible también para leer online.

Abstract: Young stars are formed within dusty discs. The grains in the disc areoriginally of the same size as interstellar dust. Models predict that thesegrains will grow in size through coagulation. Observations of the silicatefeatures at micron wavelengths are consistent with growth to micron sizeswhereas the slope of the SED at longer wavelengths traces growth up to mmsizes. We here look for a correlation between these two grain growthindicators. A large sample of T-Tauri and Herbig-Ae-Be stars was observed withthe Spitzer Space Telescope at 5-13 micron; a subsample was observed at mmwavelengths. We complement this subsample with data from the literature tomaximise the overlap between micron and mm observations and search forcorrelations. Synthetic spectra are produced to determine which processes mayproduce the dust evolution. Dust disc masses in the range <1 to 7 x 10^-4 MSunare obtained. Most sources have a mm spectral slope consistent with graingrowth. There is a tentative correlation between the 10-micron silicate featureand the mm slope of the SED. The observed sources seem to be grouped perstar-forming region in the micron-vs-mm diagram. The modelling results showthat the 10-micron feature becomes flatter and subsequently the mm slopebecomes shallower. Grain size distributions shallower than that of the ISMand-or bright central stars are required to explain specific features. Settlingof larger grains towards the disc midplane affects the 10-micron feature, buthardly the mm slope. The tentative correlation between the strength of the10-micron feature and the mm slope suggests that the inner and outer discevolve simultaneously. Dust with a mass dominated by mm-sized grains isrequired to explain the shallowest mm slopes. Other processes besides graingrowth may also be responsible for the removal of small grains.



Autor: Dave J. P. Lommen, Ewine F. van Dishoeck, Chris M. Wright, Sarah T. Maddison, Michiel Min, David J. Wilner, Demerese M. Salter, H

Fuente: https://arxiv.org/



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