Astronomy and Astrophysics – Astronomy
Scientific paper
Feb 2005
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2005aipc..745..388t&link_type=abstract
HIGH ENERGY GAMMA-RAY ASTRONOMY: 2nd International Symposium on High Energy Gamma-Ray Astronomy. AIP Conference Proceedings, Vo
Astronomy and Astrophysics
Astronomy
Supernova Remnants, Far Infrared
Scientific paper
ISOPHOT far-infrared and SCUBA sub-mm images of the Crab nebula are presented. The ISOPHOT observations were made in the bands centred at 60, 100, 170 μm, with FWHM of equivalent area Gaussian beams of 44, 47 and 93 arcsec, respectively. The 850 μm SCUBA image was processed using a Maximum Entropy Method algorithm and has a Gaussian FWHM of 17 arcsec. The 60 and 100 μm images show clear excess of emission, above that expected from an extrapolation of the synchrotron spectrum of the Crab nebula from lower frequencies, as previously seen from IRAS observations. The superior angular resolution of the ISOPHOT images reveal that about half this excess is attributable to two peaks, separated by ~ 80 arcsec. The lower resolution 170 μm image does not show any excess emission, but is possibly fainter, particularly in the NW, than expected from an extrapolation of the lower-frequency synchrotron emission. These findings are consistent with a picture in which the FIR excess is due to emission from a small amount of warm dust (of the order of hundredths of a Solar mass) which radiates predominantly at 60 and 100 μm micron but not at 170 μm, superimposed on a synchrotron spectrum which gradually steepens towards shorter wavelengths throughout the FIR and MIR spectral range. The dust geometry is consistent with a torus of diameter ~ 0.8 pc created by the supernova progenitor, superimposed upon a broadly distributed component which may be supernova condensates in the filaments. Comparison of the 850-μm image with longer wavelength radio observations shows there is little variation in spectral index of the synchrotron emission across the face of the remnant.
Green David A.
Popescu Costin
Tuffs Richard. J.
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