Very cold dust associated with molecular gas.
R. J. Laureijs, L. Haikala, M. Burgdorf, F. O. Clark, T. Liljestroem, K. Mattila, T. Prusti;
AaA, 1996, 315, 317
ABSTRACT:We report the detection of very cold dust in a small and isolated dust cloud.
Observations at 60, 90, 135, and 200{mu}m show a constant surface brightness ratio
I_135_/I_200_ and a flattening of I_90_/I_200_ towards the cloud centre.
The dust
temperature derived from the far-infrared colours can be confined to the range of
12-15K assuming a {lambda}^-2^ dust emissivity.
The 60{mu}m emission comes
mainly from outer dust layers surrounding the core.
We infer that a fraction
of the power in the 90{mu}m band comes from the warmer grain component also
causing I_60_.
This fraction is approximately equal to the total power in the
60{mu}m band.
The cloud is also detected in ^12^CO, ^13^CO, CO^18^, HCO^+^ and
CS.
The detections indicate that the dust emission is associated with a
molecular cloud core where n(H_2_) >=3x10^4^cm^-3^.
Using the column density
derived from the molecular observations we find an extinction cross section
per H-atom of 4.1-9.5cm^2^/H-atom.
KEYWORDS: interstellar medium: dust, extinction, interstellar medium: clouds, interstellar medium: molecules
PERSOKEY:dust, ,
CODE: laureijs96