Radio versus X-ray surface brightness correlation for the halo in Abell 2256 at 144 MHz (left) and 675 MHz (Right). Images and fitting is the same as in Fig. 8 but including all regions where both radio and X-ray surface brightness exceeds 2σ (emission below 3σ is shown as upper limits). Correlation between the radio and X-ray surface brightness across the halo region gets tighter when including all the halo emission at low frequencies. The best-fitted correlation slopes are b_144 MHz = 0.87 ± 0.02, b_675 MHz = 0.88 ± 0.03 in the halo region. The data points from the wedge arc are not scattered but are above the halo correlation.