1 CEA Saclay, SAp, France
Today we have to ability to observe high-redshift galaxies allowing us
to study the early stages of galaxy formation and evolution in the
universe. The observed characteristics of the objects in the deep
field images are a matter of debate, and one interpretation suggests a
population of star-forming dwarf galaxies at high-redshifts
(eg. Colley et al, 1997). We have taken advantage of the large variety
of low-metallicity dwarf galaxies residing in the local universe
through an ISOCAM survey to study the dust content and the
characteristics of their MIR emission. These are proving to be ideal
laboratories with which to investigate the relationship between the
ISM and starformation in low-metallicity environments. This knowledge
can then be applied to the interpretation of primeval dwarf galaxies.
We will present, for example, ISOCAM CVF observations of the 3 dwarf galaxies, IIZw40, NGC1569 and NGC1140, representing a range of star formation, metallicity and morphological properties. PAH features, ionic lines and hot grain continuum emission are present in the MIR spectra. This sample provides example of a sequence of PAH features/continuum emission ratios that increases from IIZw40 to NGC1569 and NGC1140. We attempt to explain the spectra with a dust model that is characterized by a combination of HII regions, photodissociation regions and molecular clouds.