Infrared emissions from spherical dust, clouds are calculated using quasi-diffusion method. We have employed graphite-silicate mixture with power-law size distribution for the dust model. The grains are assumed to be heated and cooled by radiative processes only. The primary heating source is diffuse interstellar radiation field. hut the cases with an embedded source are also considered. Since graphite grains have higher temperature than silicate grains, the observed IR emission is mainly due to graphite grains, unless the fraction of graphite grains is negligibly small. The color temperature of Bok globules obtained from IRAS 60 and 100 μ m data are found to be consistent with the dust cloud with graphite-silicate mixture exposed to average interstellar radiation field. The color temperature is sensitive to the external radiation field, but rather insensitive to the size distribution of the grains. We found that the density distribution can be recovered outside the beam size using the inversion technique that assumes negligible optical depth. However, the information within the beam size is lost for if beam convolved intensity distributions are used in deriving density profile.

ABSTRACT
Ⅰ. INTRODUCTION
Ⅱ. METHOD OF CALCULATION
Ⅲ. MODELS FOR THE DUST CLOUDS AND ASSUMPTIONS
Ⅳ. DUST CLOUD HEATED BY ISRF ONLY
Ⅴ. DUST CLOUDS WITH AN EMBEDDED SOURCE
Ⅵ. DENSITY DISTRIBUTION FROM SURFACE BRIGHTNESS
Ⅶ. SUMMARY AND CONCLUSIONS
ACKNOWLEDGEMENTS
REFERENCES

• LEE SANG-GAK(Department of Astronomy, Seoul National University)
• YUN HONG SIK(Department of Astronomy, Seoul National University)
• HONG SEUNG SOO(Department of Astronomy, Seoul National University)
• LEE HYUNG MOK(Department of Earth Sciences, Pusan University)