DUST EMISSION AS A QUANTITATIVE PROBE OF STAR-FORMING REGIONS

This article discusses thermal emission from interstellar dust as a quantitative probe of gas in star-forming regions, with particular emphasis on the interpretation of observations made at millimeter and submillimeter wavelengths. Expressions relating dust opacity to the column density of hydrogen are derived. Examination of the uncertainties associated with the observations and with intepretation shows that beam-averaged hydrogen column densities in these regions can be determined within factors of 5-20. The largest source of uncertainty lies in the conversion of derived dust opacities into gas column densities. Within the wavelength range 100 < lambda < 3000 mu m, we suggest the relationship N(H)/tau(dust) approximate to 1.1 x 10(20)lambda(2.0) cm(-2) for dense dust clouds until the nature of the dust grains within these clouds becomes better known.