Left: GMRT 325 MHz radio contours of A 209 at full resolution (11.0′′ × 8.7′′, p.a. 30°), overlaid on the optical POSS-2 image. The 1σ level in the radio image is 0.12 mJy beam^-1 and red contours are spaced by a factor 2 starting from +3σ = 0.36 mJy beam^-1. Black dashed contours correspond to the − 3σ level. Labels S1 and S2 show are the radio galaxies embedded in the radio halo emission. Right: GMRT 325 MHz radio contours at the resolution of 25.0′′ × 25.0′′, p.a. 0°, superposed to the smoothed Chandra X-ray image. No source subtraction has been performed. White contours start at + 3σ = 0.9 mJy beam^-1 and then scale by a factor 2. The − 3σ level is shown as red dashed contours.