The following document lists the file abstract/DKUNTH_PAHDWARF.abs
from catalogue VI/111.
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We have selected a sample of star-forming galaxies and giant HII regions in which star formation processes are vigorous. This sample has been well studied at all wavelengths allowing a good knowledge of the star-formation rates hence the ionizing radiation field produced by newly born massive stars. The metallicity of the interstellar gas is also well known and ranges from 1/30Z(solar) to Z(solar). In addition, the sample has been thoroughly studied with IUE. UV-optical spectra have been analysed and provide the shape of the extinction curve needed to fit the data assuming a burst of star formation. This revealed that the extinction curve is markedly different from the Galactic one and closer to the LMC or SMC ones, ie very small or no bump at 2175 A, and nearly linear UV rise. The aim of our observations is to try and understand the reason of this marked difference: is the high UV field destroying some of the dust components? is it affecting the size distribution? Is the lower metallicity affecting the dust content of these regions on the large scale? These questions can be answered by mapping the PAH lines, as their intensities are linearly linked to both their abundance and to the intensity of the UV field. Indeed, since the UV source distribution is well known, the spatial distribution of PAH emission will tell us whether the dust is affected more by destruction processes, or if the formation rates are lower due to a lower metallicity. Furthermore, these maps will allow a clear statement of which part of the extinction curve is indeed associated with PAH molecules, as this is still a matter of controversy.