Radio luminosity profile across the width of relic RE. Solid line displays the 1382 MHz luminosity profile, averaged over the full 1.4 Mpc extent, of the relic RE. Dashed line displays the resulting spectral index profile (labeling on the right axis), also averaged over the full 1.4 Mpc extent, between 1382 and 241 MHz. The averaging was done by adding up the total flux at each frequency in a spherical shell and then calculating the spectral index.