IRAS detection of very cold dust in the Lynds 134 cloud complex
R. J. Laureijs, F. O. Clark, T. Prusti;
ApJ, 1991, 372, 185
ABSTRACT:IRAS maps at 60 and 100 microns of the complex of dark clouds containing L1345, L183, and L1780 are presented and discussed.
Extended regions are
apparent where the 60 micron emission is very low compared to the 100 micron
emission.
The 60-100 micron flux ratio has a constant value of 0.2 in the outer diffuse
parts of the clouds but suddenly drops to less than 0.03 in the opaque cloud
centers.
A geometrical model is used to show that the drop occurs in a narrow
transition layer that has not been resolved by IRAS.
The observations provide
direct evidence for dust temperatures colder than 15 K in dark clouds.
A
number of 60 micron-deficient regions are defined using the quantity Delta
I(100) = I(60)/Theta, where Theta is the ratio I(60)/I(100) in the diffuse
parts of the complex.
Delta I(100) is highly proportional to extinction and
(C-13)O column density.
The relationships indicate that the dust
temperature must be constant over a large fraction of the volume sampled by Delta
I(100).
An upper limit of 4.8 g/sq cm is obtained for the mass absorption
coefficient of dust at 100 microns.
KEYWORDS: cosmic dust, dark matter, infrared sources (astronomy), molecular clouds, emission spectra, infrared astronomy satellite, interstellar matter, nebulae
PERSOKEY:dust, iras, fir, molecular clouds, ,
CODE: laureijs91