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Accueil > Séminaires > Archive des séminaires d’Utinam > Archive des séminaires d’astrophysique (jusqu’en 2011) > 2010

The AGB Dust Mass-Loss Return to The LMC Using SAGE Data

par Edith Burgey -

Lundi 29 mars 2010

Sundar Srinivasan

Institut d’Astrophysique de Paris

Résumé :

The asymptotic giant branch (AGB) phase is the penultimate stage of evolution for low- and intermediate-mass stars. AGB stars are responsible for massive dust and gas outflows at rates exceeding their nuclear burning rate, thereby injecting a significant fraction of their mass into the surrounding interstellar medium (ISM) and seeding newly-forming stars. The study of AGB mass loss is therefore essential for understanding the chemical evolution of galaxies as a whole. The Large Magellanic Cloud (LMC) is an excellent candidate for such studies. Data from the Spitzer SAGE survey provides us with multi-band photometry of about 30,000 AGB candidates. A rough estimate for the total AGB injection rate, obtained from studying the infrared excesses of these stars, is (6-13)x10-3 Msun/yr, the majority of which is due to the so-called "extreme" AGB stars. I present a grid of models for carbon-rich AGB stars generated by the radiative transfer (RT) code 2DUST. These models span a range of different effective temperatures and gravities as well as dust shell radii and optical depths. I obtain a baseline set of dust properties for use in the model grid from RT modeling of a single carbon star, data for which was acquired as part of the spectroscopic follow-up to SAGE. The model grid enables, for example, a more precise determination of the AGB injection rate. AGB stars are the best laboratories for the study of dust grains, and the development of a model grid is a huge step towards understanding the role of AGB stars in galaxies.