The following document lists the file abstract/RTUFFS_SNR.abs
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SCIENTIFIC ABSTRACT We propose a spectrophotometric and spectropolarimetric investigation of the prototype young galactic supernova remnants Cas A and the Crab Nebula, respectively. This investigation addresses the possible formation, composition and destruction of grains in these objects, the properties of dust and gas in the pre-existing circum-progenitor media (CPM), and the chemical composition and dynamics of the ejecta. We further propose to study the early stages in the evolution of the remnant of SN1987A, which could be a brightening infrared source during the lifetime of ISO. In the event of an autumn launch the Crab Nebula will be not visible to ISO, and we intead propose an investigation of the shock processing of interstellar grains at the blast wave of the Cygnus Loop. OBSERVATION SUMMARY Using PHT-C we propose to measure several positions within the Crab Nebula in it's polarised synchrotron emission at 12, 25, 60 and 100 micron. This addresses the question of the origin of the ``bump'' in the FIR spectrum detected by IRAS. The positions for polarimetry are chosen to be at positions of different magnetic field orientations as revealed from maps of the radio synchrotron emission. Oversampled absolute photometric mapping in total power at 60, 100, and 200 micron will be achieved by concatenating linear scans taken in the absolute photometry mode to two dimensional mapping observations. This will establish the integrated spectrum of the nebula in the FIR, and will measure the spatial distribution of mass column densities and temperatures of the grains in the nebula. Spectrophotometric mapping of the entire nebula using PHT-S will probe the chemical composition of the grains, and provide a survey of line emission from more highly ionised species in the photoionised gas than can be seen in the UV and visible. These measurements are complemented by the ISOCAM mapping of the nebula by Lagage et al. PHT-C diffraction-limited mapping of Cas A at 200, 160, 100 and 60 micron should provide a definitive measurement of the mass of any grains present in unshocked, cold dense regions of the metal rich ejecta, which should be mainly interior to the hot component of emission collisionally heated by shocked gas in the shell of the remnant. PHT-S mapping will probe the location and compositions of the ejecta and circumprogenitor medium, both in the gas and solid state components. A particular aim is to investigate the possible presence of gas components with densities and temperatures intermediate between those found in the dense fast optical filaments and the diffuse X-ray emitting plasma. The spectral resolution of approximately 3000 kms**-1 should provide information on the pattern of velocities of ejected species emitting infared fine structure line emission. A map with a finer raster will be made with PHT-S towards the complex of fast optical filaments outside the shell to the North-East. A deeper single pointing will be made with PHT-S towards the expansion centre of the remnant. These observations are complementary to the ISOCAM mapping observations of Cas A proposed by Lagage et al. The remnant of SN1987A will be observed with the PHT-C100 and PHT-C200 arrays in the C60, C90, C160 and C180 filters to measure any dust from the ejecta/ circumprogenitor medium in the 10 - 30 K temperature range. To lower the FIR confusion limit from interstellar dust emission from the LMC, spatially oversampled scans will be taken through the source. Warmer dust associated with the blast wave/shocked gas will be searched for using the PHT-P2 detector with the 25 micron filter at a fixed spacecraft raster position with the focal plane chopper in it's triangular mode. Optimum sensitivity and angular resolution for broad-band emission from the supernova/cpm in 12-18 micron range will be provided by ISOCAM using it's smallest pixel size and longest readout interval. The ISOCAM image will also be sensitive to echo emission structures from the interstellar medium around the supernova. The limiting rms flux densities to point sources reached in the 12-18/25/60/90/160/180 micron filters is predicted to be approximately 0.01/8/3/1/3/4 mJy respectively. Continuued in scientific justification section...