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

Abstract

We present subarcminute-resolution (≈10''), high-dynamic range radio observations of Tycho's supernova remnant (3C 10) at λ = 20 cm and λ = 90 cm with the Very Large Array (VLA). The thermal-noise-limited 90 cm image has been compensated properly for the noncoplanar characteristics of the VLA and is the most sensitive low-frequency image of this source presently available. We use these images to search for spatial variations in the continuum radio spectral index within the remnant. Such spatial variations should be related to the electron acceleration processes associated with the evolution of the blast wave. We have also utilized, for the first time in an analysis of a supernova remnant, spectral tomography to search for localized regions within which the spectral index is different from the surroundings. We have identified 13 filaments, ranging in size from ≈40'' to ≈260'', embedded in a smoother, background component. The average spectral index of the filaments ( = -0.52 ± 0.02) is consistent with that of the background component ( = -0.500 ± 0.007). However, the filaments in the outer rim show a trend such that 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 hypotheses could be tested by an image at comparable resolution and fidelity at a third frequency.