Dust distribution in galactic compact HII regions
Abstract
We present the first results of an Open Time ISOCAM program aiming to look at the distribution of the Infrared Emission Features (IEFs) and the associated continua between 3 and 12 \ensuremathμm in five galactic compact HII regions. The idea is to add new observational constraints on the IEF carriers. The peak location of the IEFs is always found at the interface between ionized and neutral media. The continuum contribution is high near the main exciting star. The (band+continuum) intensity ratios show important variations. However, in all regions and for a given ratio, the same value is found at specific locations of the interface. This result points out the interface as a `privileged' zone for the study of IEF properties. Finally, a strong rising continuum is observed between 10 and 12 \ensuremathμm. This continuum probably corresponds to the short wavelength part of the thermal emission from cold grains (T\raisebox-0.5ex~= 40 K) that peaks around 70 \ensuremathμm in compact HII regions.