===> In this proposal, more time is being requested for KSELLGRE.REFNEB_1.
===> Some time for this proposal is to be transferred from KSELLGRE.REFNEB_1.
In the first call for ISO proposals we were awarded time to observe 5
reflection nebulae (RN), with ISOCAM, in order to determine the spatial
distribution of specific infrared emission features (IEFs) within each RN.  We
have successfully detected IEFs (Fig. 1) in a RN whose central star (Tstar =
6,800K) produces very little ultraviolet radiation, a remarkable result posing
problems for PAH models.  We propose to follow up on these findings by
observing 1 new RN (similar in terms of its cool illuminating star) and by
better positioning 3 others previously observed.  We also propose to replace
scheduled observations of a faint RN with a brighter RN of similar Tstar, and
observe another new RN (both possible only because of the ISO extended
lifetime), to extend our range of illuminating star temperatures.  As with
the original observing strategy, we plan to obtain multi-wavelength CVF images
to study the various IEFs and the 6-9 um and 11-13 um broad spectral features;
CVF images at continuum wavelengths of 9.5 and 10.5 um; and broad-band
continuum images at 4.5 um (LW1) and 15.0 um (LW9).
Our goals are to obtain ISOCAM images with the CVF in RN with widely varying
Tstar to: (1) determine the photon energies required to excite different IEFs
and the continuum, and (2) study the effects of ionizing radiation, PAH size
distribution, PAH charge, and PAH hydrogenation on the spatial distributions of
different IEFs and the continuum.  Each of these observations will be compared
to model predictions for polycyclic aromatic molecules, hydrogenated amorphous
carbon grains, and other laboratory materials.  ISOCAM observations are needed
because of its superb sensitivity to low surface brightness mid-infrared
emission, which is far higher than the sensitivity achievable from ambient
temperature ground-based or airborne telescopes.