The following document lists the file abstract/CWRIGHT_CWRIGH_2.abs
from catalogue VI/111.
A plain copy of the file
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Observations of molecular ices on interstellar dust grains
can be used to constrain the physical conditions that were
present when the ice first formed. This has already been done in
a limited way using the 3.1 um stretching vibration of the most
abundant ice, H_2O (Smith et al., 1989, ApJ 344, 413). However,
the other vibrations of H_2O ice can also provide important and
unique information. We are proposing to use the ISO Long
Wavelength Spectrometer (LWS) to investigate two key problems
relating to the formation of icy mantles and the nature of grain
surfaces, by observing the far-infrared translational-mode
spectrum of H_2O ice in a small, carefully selected sample of
objects.
The primary objective of this proposal is to measure the
relative strengths of three of the translational mode features
in the far-infrared spectrum of H_2O ice; these fall at 44 um,
62 um and 165 um. The 44/62 um peak ratio is indicative of the
formation conditions of the ice and can be used to trace the
temperature history of the dust, e.g. whether it was initially
deposited at low temperatures and then warmed up (as might
occur when a protostar forms in a molecular cloud) or whether
it was initially deposited at high temperatures and then cooled
(as might occur in a circumstellar envelope). On the other
hand, the strength or even the presence of the 165 um feature
seems to be dependant on the nature of the grain surface.
In conjunction with existing and ongoing laboratory work we
can use the proposed observations to provide a powerful tool for
studying the formation of icy grain mantles and the nature of
the surfaces they were formed on.