Spectral energy distribution of three regions, showing that only region A has significant (> 2σ) curvature. Labels in the plot correspond to the regions labelled in Fig. 4. Left: lines are a least-squares polynomial fit through the data in order to give an indication of the steepness of the spectra. The spectra indicate that region A is the steepest. Right: piecewise spectral indices of the three regions, including error. In the top-right corner, the difference between the spectral index at the highest frequency and the spectral index at the lowest frequency is given.