International Conference on Interstellar Dust, Molecules and Chemistry

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The interstellar medium (ISM) consists of a mixture of ions, atoms, molecules, dust grains, cosmic rays, and (galactic) magnetic fields. Thus it is a treasure trove for the study of a wide variety of physical phenomenon. The ISM also plays a crucial role in star and planet formation. The interplay between stars and the ISM determines the lifespan of active star formation and evolution. Recent advances in observational, laboratory, theoretical studies have opened up several avenues of work, made attractive by the possibilities of diverse interdisciplinary interactions. The conference intends to provide platform for expert discussions and presentations with ample opportunities for young and motivated students and researchers to interact and to take up challenging problems in this field. Broad Topics: i) ISM Overview - Constituents, Observational diagnostics ii) Dust in ISM - Composition, Starlight extinction - observations & models iii) ISM Molecules and Spectroscopy iv) Star Formation - The Role of the ISM v) Dust and molecules in external galaxies vi) Laboratory Astrophysics and Astrochemistry vii) Quantum Chemistry

We present a composite grain model to explain the IR emission features at 10 and 18 µm from the circumstellar dust of stars. The IRAS-LRS data from about 700 stars have been analysed and fitted to a set of composite porous dust grains consisting silicate host and graphite/vacuum nclusions. The 10 µm silicate feature shifts with the inclusion volume fraction of graphite grains but not with the changes in porosity. Both 10 and 18 µm features do not broaden with the inclusions of graphite or vacuum. It is also noted that the axial ratio of the dust grain shapes change for various types of circumstellar dust observed in the IRAS data.The model uses a composite fluffy dust grain for ex-plaining most of the observed interstellar extinction curves and also polarization. Another parameter which needs to be constrained by the dust models is the in-terstellar abundances of Carbon and Silicon which is usually overestimated by the solid dust models but our model predicts closer match to the observed ISM abun-dances. Further, our composite dust model also ex-plains the IR emission from circumstellar dust.

International Conference on Interstellar Dust, Molecules and Chemistry

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