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The properties and evolution of large and cold dust particles between the stars – Cold Dust

Submission summary

A major and long-standing puzzle in astrophysics is the exact nature of the large interstellar grains that contain the bulk of the dust mass. From the interstellar medium (ISM) in nearby star forming regions to the ISM in distant galaxies it is the observed Far-IR to mm wavelength (FIR-mm) thermal emission from the large and cold dust grains, at temperatures of 10-20 K, that dominates the dust thermal emission spectrum. Currently we do not understand the detailed physics of this long wavelength emission coming from such cold matter because we lack the necessary physical models and the laboratory data to constrain these models. A real challenge is therefore going to be presented to astronomers by the FIR-mm galactic, extra-galactic and cosmological observations that will be made with the Herschel and Planck space observatories, due for launch in 2008/2009. It is therefore timely that we propose to launch a targeted, multidisciplinary modelling and laboratory programme to understand the nature of the large, cold grains, their evolution within the context of the physical and chemical evolution of interstellar matter, and the physics of the FIR-mm emission process.

The principal result expected from this project is a self-consistent model for the properties and evolution of the dust in the ISM in terms of the dust microscopic properties and its macroscopic evolution in the local environment that will then be linked to the calculation of the FIR-mm spectra. The analysis of observations, the development of new modelling tools with new predictive capabilities, and the development of a new experimental set-up are the key and complementary elements of this proposal. At the end of the ANR we plan to provide astronomers with the necessary tools to analyse observational data in the FIR-mm wavelength regime. These tools will be particularly important in determining, and subtracting, the galactic foreground 'contamination' in extragalactic and cosmological observations.

The first objective of our project is to further our understanding of the microscopic grain properties (composition, shape, structure, low temperature behaviour) and their macroscopic evolution in the local interstellar environment (size distribution modifications due to the effects of coagulation and fragmentation). The second objective is to apply, within the astrophysical context, our newly-gained knowledge on the physics of solids to the FIR-mm emission of amorphous solids at low temperatures. In order to achieve this we will build upon the complementary strengths of the two participating institutes (the IAS in Orsay and the CESR in Toulouse). The work of this project falls into two broad, but necessarily overlapping, subject areas: 1) an observational and modelling program based primarily at the IAS and 2) an experimental and theoretical program based primarily at the CESR.

The IAS team will extract from observations (e.g., Spitzer, WMAP, …) constraints on the nature and evolution of interstellar grains. In parallel we will model the evolutionary processes that act on dust to determine their micro- and macro-scopic properties, e.g., coagulation and fragmentation in turbulent interstellar clouds. The CESR team will model the low temperature, solid-state physics of amorphous materials, calculate their FIR-mm optical properties and develop a new experimental facility to allow a validation of the theoretical approach and to provide realistic input parameters for astrophysical models. We request two ANR-funded Post docs. each one for a period of three years, one to be based at the IAS (to work predominantly on the astrophysical modelling in area 1) and the other to be based at the CESR (to work predominantly on the fundamental physics in area 2). The two Post docs. will work very closely together and will be expected to actively lead and coordinate aspects of the ANR-related activities at the IAS and the CESR for which we currently lack expertise. This new and complementary experience that the post docs. will bring to each institute, their role developing these new research projects and, their critical role in coordinating this project, in conjunction with the two PIs (A. Jones, IAS and C. Meny, CESR), will help to put our teams, as well as the French astronomical community, in a leading position in the study of cold dust.

The PIs at each institute (Anthony Jones, IAS; Claude Meny, CESR) will dedicate most of their available research time to this important and key project.

Project coordination

Anthony JONES (Organisme de recherche)

The author of this summary is the project coordinator, who is responsible for the content of this summary. The ANR declines any responsibility as for its contents.

Partner

Help of the ANR 270,000 euros
Beginning and duration of the scientific project: - 36 Months

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