Abstract
The upper limit for the absorption cross section σ ext H , of dust in Hii regions in the wave-length range 912–504 Å derived by Mezgeret al. (1974), is compatible with that expected for large dust grains, and a gas-to-dust ratio equal to that in the general interstellar medium. The albedo of the small grains must be high for λ>504 Å. This restriction is lifted if the visual extinction cross section of the grains in Hii regions is less than that for grains in the general interstellar medium. New observations of the Orion Nebula indicate that the visual extinction cross section is within a factor 2 of the value in the general interstellar medium.
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Smith, L.F. A review of recent observations of dust in Hii regions. Astrophys Space Sci 34, 49–55 (1975). https://doi.org/10.1007/BF00646747
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DOI: https://doi.org/10.1007/BF00646747