Spectral index map of the minihalo of the Perseus cluster between 44 and 144 MHz. The HBA map has been smoothed to the resolution of the native LBA map. The associated spectral index uncertainty map is displayed in Fig. C.2. We note that 3C 84 is located at the centre, and it has been blanked out for clarity. The red circles refer to the ghost cavities whose spectra are shown in Fig. 6. The noise in this image is higher than the noise reported in Table 1 due to the proximity of 3C 84.