Swinburne
Browse

Grain growth across protoplanetary discs: 10 μ m silicate feature versus millimetre slope

Download (939.94 kB)
journal contribution
posted on 2024-08-06, 09:13 authored by D. J. P. Lommen, E. F. van Dishoeck, C. M. Wright, Sarah MaddisonSarah Maddison, M. Min, D. J. Wilner, D. M. Salter, H. J. van Langevelde, T. L. Bourke, R. F. J. van der Burg, G. A. Blake
Young stars are formed with dusty discs around them. The dust grains in the disc are originally of the same size as interstellar dust, i.e., of the order of 0.1 μm. Models predict that these grains will grow in size through coagulation. Observations of the silicate features around 10 and 20 μm are consistent with growth from submicron to micron sizes in selected sources whereas the slope of the spectral energy distribution (SED) at mm and cm wavelengths traces growth up to mm sizes and larger. We here look for a correlation between these two grain growth indicators. A large sample of T-Tauri and Herbig-Ae/Be stars, spread over the star-forming regions in Chamaeleon, Lupus, Serpens, Corona Australis, and the Gum nebula in Vela, was observed with the Spitzer Space Telescope at 5–13 μm, and a subsample was observed with the SMA, ATCA, CARMA, and VLA at mm wavelengths. We complement this subsample with data from the literature to maximise the overlap between μm and mm observations and search for correlations in the grain-growth signatures. Synthetic spectra are produced to determine which processes may produce the dust evolution observed in protoplanetary discs. Dust disc masses in the range <1 to 7x10-4 M_o are obtained. The majority of the sources have a mm spectral slope consistent with grain growth. There is a tentative correlation between the strength and the shape of the 10-μm silicate feature and the slope of the SED between 1 and 3 mm. The observed sources seem to be grouped per star-forming region in the 10-μm-feature vs. mm-slope diagram. The modelling results show that, if only the maximum grain size is increased, first the 10-μm feature becomes flatter and subsequently the mm slope becomes shallower. To explain the sources with the shallowest mm slopes, a grain size distribution shallower than that of the interstellar medium is required. Furthermore, the strongest 10-μm features can only be explained with bright (L ~ 6 L_o), hot (Teff = 4000 K) central stars. Settling of larger grains towards the disc midplane results in a stronger 10-μm feature, but has a very limited effect on the mm slope. A tentative correlation between the strength of the 10-μm feature and the mm slope is found, which would imply that the inner and outer disc evolve simultaneously. Dust with a mass dominated by large, ~mm-sized, grains is required to explain the shallowest mm slopes. Other processes besides grain growth, such as the clearing of an inner disc by binary interaction, may also be responsible for the removal of small grains. Observations with future telescopes with larger bandwidths or collecting areas are required to provide the necessary statistics to study these processes of disc and dust evolution.

History

Available versions

PDF (Published version)

ISSN

0004-6361

Journal title

Astronomy and Astrophysics

Volume

515

Issue

9

Article number

article no. A77

Pagination

26 pp

Publisher

EDP Sciences

Copyright statement

Copyright © 2010 ESO. The published version is reproduced in accordance with the copyright policy of the publisher.

Language

eng

Usage metrics

    Publications

    Categories

    No categories selected

    Keywords

    Exports

    RefWorks
    BibTeX
    Ref. manager
    Endnote
    DataCite
    NLM
    DC