High-resolution spectral index map of A1033. Left image: spectral index between 54 and 144 MHz, and right image: same between 144 and 323 MHz (center). The images are on the same color scale and have an angular resolution of 12″ × 9″. Upper limits below −1.6 are outside the black contours and marked by arrows. The saturation scales inversely with the uncertainty on the spectral index. Right image: corresponding curvature map, defined as the difference .