Contents of: VI/111/./abstract/JGURTLER_DUSTABS.abs

The following document lists the file abstract/JGURTLER_DUSTABS.abs from catalogue VI/111.
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SCIENTIFIC ABSTRACT
In order to determine the composition of the dust in various types of clouds,
e.g. molecular and diffuse clouds, we propose to measure the absorption 
spectra of large samples of (a) sources embedded in clouds, (b) stars located
in the background of clouds, and (c) highly reddened field stars. Emphasis is
placed on the study of ices (e.g. that of H2O, CO2, CO) and silicates. The
optical depths of the absorption features of the various ices compared to that
of the silicates allow to derive the chemical and physical conditions 
(e.g. temperature) within the clouds and to study the coagulation and 
accretion of dust grains. Attempts will be made to determine the intrinsic 
spectra of the embedded sources.

OBSERVATION SUMMARY
We want to study the chemical composition of dust in various
clouds. For this purpose we selected a set of embedded sources
from the literature (e.g., the IRAS Point Source Catalogue) and
added a number of highly reddened stars to probe lines of sight
through the diffuse interstellar medium as well as through
several dark clouds. The spectra of the proposed sources will be
recorded with PHT-S (AOT P40). The integration time is determined by
the requirement of a S/N of at least 20 with the exception of the strongest
absorption bands in a very limited number of sources.


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