| 日時: | 2012 年 3 月 14 日(水) 16:30-17:00 |
| 場所: | CPS セミナー室 |
| 講演者: | Ranjan Gupta (IUCAA) |
| 世話人: | 伊藤 洋一 |
| タイトル: | NIR Silicate features and Statistics from IRAS data |
| abstract: |
We present a composite grain model to explain the IR
emission features at 10 and 18 microns 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 inclusions. The 10 micron silicate feature
shifts with the inclusion volume fraction of graphite grains
but not with the changes in porosity. Both 10 and 18 micron
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 explaining most of the observed interstellar extinction curves and also polarization. Another parameter which needs to be constrained by the dust models is the interstellar abundances of Carbon and Silicon which is usually overestimated by the solid dust models but our model predicts closer match to the observed ISM abundances. Further, our composite dust model also explains the IR emission from circumstellar dust. |
| キーワード: | Dust, Extinction, Circumstellar Matter |