The following document lists the file abstract/KSELLGRE_RN_TSTAR.abs
from catalogue VI/111.
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===> 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.