Spatial variations of the synchrotron spectrum within Tycho's supernova remnant (3C 10): A spectral tomography analysis of radio observations at 20 and 90 centimeter wavelengths

We present subarcminute-resolution (approximate to 10 "), high-dynamic rang e radio observations of Tycho's supernova remnant (3C 10) at lambda = 20 cm and lambda = 90 cm with the Very Large Array (VLA). The thermal-noise-limi ted 90 cm image has been compensated properly for the noncoplanar character istics of the VLA and is the most sensitive low-frequency image of this sou rce presently available. We use these images to search for spatial variatio ns in the continuum radio spectral index within the remnant. Such spatial v ariations should be related to the electron acceleration processes associat ed with the evolution of the blast wave. We have also utilized, for the fir st time in an analysis of a supernova remnant, spectral tomography to searc h for localized regions within which the spectral index is different from t he surroundings. We have identified 13 filaments, ranging in size from appr oximate to 40 " to approximate to 260 ", embedded in a smoother, background component. The average spectral index of the filaments ([alpha] = -0.52 +/ - 0.02) is consistent with that of the background component ([alpha] = -0.5 00 +/- 0.007). However, the filaments in the outer rim show a trend such th at brighter filaments have a flatter spectral index. This trend may be due to either supernova remnant (SNR) blast wave-ambient medium interactions or internal inhomogeneities of the magnetic field within the remnant. These h ypotheses could be tested by an image at comparable resolution and fidelity at a third frequency.