Observatoire de Marseille, 2 place Leverrier, 13248 Marseille Cedex 04, France
A series of emission bands, the so-called unidentified infrared bands
UIRBs, is seen in various astrophysical sources between
3 and 16 
.
These bands are commonly attributed to
carbonaceous compounds. However, of the varisou candidates that have been
proposed as carriers of these emission bands (and possibly part of the
mid-infrared emission continuum), none has yet provided a fully
satisfactory match to all the observed characteristics. More laboratory
work together with astronomical observations are needed to better constrain
the identification of the carriers. For this purpose, we selected a sample of
five compact galactic HII regions, spanning a large range in physical
conditions (spectral type and evolution state of the exciting star, distance).
With ISOCAM and the 3
pixel field of view, a mapping
of the UIRBs and continuum emission distributions is done in these regions
using dedicated filters for the UIRBs (SW1, SW2, LW4, LW6, LW8) and the
circular variable filter at 6, 6.9, 8.2, 10.5, and 12
for the
continuum measurements. the presence of atomic fine-structure lines of
[ArII] and [SIV] in this range also allows a mapping of the physical
conditinos in these regions.
We present the results of the ISOCAM observations for the five compact HII regions and discuss the contribution of this work towards the identification of the UIRB carriers. ISOGAL images of some of these fields (see Omont et al. and Copet et al., this conference) together with results of related ongoing projects like the search for extended red emission in these regions (see Darbon et al., this conference) will also be presented.