Spectral index distribution in six equally-numbered flux density bins at 54 MHz. In each bin, a Gaussian fit and its centre is marked and the fit details (mean and standard deviation) are in red in the top right corner. Below that, in blue, is the median, along with the 95% confidence interval ranges. In each top-left corner, the flux density limits of the bin are noted, while the black line indicates the overall mean as previously found in Fig. 10.