What are the true astronomical silicates?
Abstract
We redefine the term "astronomical silicate" by interpreting the 9.7μm and 18μm interstellar features not in terms of absorption by a pure silicate but rather in terms of silicate core-organic refractory mantle particles. The silicate core optical properties used are those of a glassy (amorphous) olivine produced in the laboratory. The optical constants of the organic refractory mantle material are derived from a combination of astronomical and laboratory spectra of residues of ultraviolet photoprocessed ices, which we define as ``astronomical organic refractory". The silicate core-organic refractory mantle elongated dust model provides an excellent match to the observation of the Becklin-Neugebauer object polarization features in shape, width, and in relative strength. An additional ice mantle is included on a fraction of the dust in the line of sight to the BN object which is consistent with the 3.1 μm absorption strength. This further improves the match to observations.
- Publication:
-
Astronomy and Astrophysics
- Pub Date:
- May 1996
- Bibcode:
- 1996A&A...309..258G
- Keywords:
-
- ISM: DUST;
- ORION: BN OBJECT;
- INFRARED;
- ISM: LINES AND BANDS;
- METHODS: LABORATORY