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