Profiles of the nonthermal spectral index, α_n, as a functionof height z above the major axis (in kpc) for the 9 strips at different distances, x, from the galaxy’s centre along the major axis. The top four panels (x > 0) correspond to the northern side of the galaxy and the bottom four panels (x < 0) to the southern side; the middle panel is centred on the minor axis. z is negative (positive) on the eastern (western) side of the halo.