Dust in HII Regions
Several pieces of evidence indicate that HII regions may contain dust: 1) the continuum light scattered by dust grains (O’Dell and Hubbard, 1965),2) thermal radiation from dust grains at infrared wavelengths (Ney and Allen, 1969), 3) the abnormal helium abundance in some HII regions (Peimbert and Costero, 1969), etc.
Although observations of the scattered continuum suggest that the HII region cores may be dust-free, dust grains and gas must be well-mixed in view of the infrared observations. This difficulty may be solved by introducing globules with sizes ~0.001 pc. These globules and the molecular clouds adjacent to HII regions are the main sources supplying dust to HII regions.
KeywordsMolecular Cloud Column Density Surface Brightness Recombination Line Radio Observation
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