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| Paper: |
New Dust Models from Recent Observational Constraints |
| Volume: |
357, The Spitzer Space Telescope: New Views of the Cosmos |
| Page: |
90 |
| Authors: |
Bernard, J.-Ph.; Boudet, N.; Meny, C.; Paradis, D.; Ristorcelli, I. |
| Abstract: |
Recent observational constraints in the FIR and sub-millimeter have shed new light upon the possible nature of the Big dust Grains (BGs) in the InterStellar Medium (ISM). The available data show a significant millimeter excess and departure from a single grey body emissivity law. The excess was attributed by several authors to the existence of very cold dust. However, it could also be due to the nature of BGs, in particular to physical phenomena arising in disordered amorphous materials at low temperature. We favor such models, which, unlike others, appear able to reproduce the correlation between the dust temperature and emissivity index evidenced in the PRONAOS data. Additional complications arise from the fact that the dust size distribution changes with physical conditions in space. For instance, the PRONAOS data indicate that, in some quiescent molecular clouds, BGs as well as the vast majority of Very Small Grains (VSGs) can coagulate into fractal aggregates. Both effect have important consequences when deriving column densities from dust emission. SPITZER /MIPS observations could contribute to strengthen our understanding of these effects. |
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