Source-subtracted images of A1550 at different frequencies. Top left: 54 MHz source-subtracted image of A1550 obtained applying Briggs −0.3 and tapering the visibilities to 30″. The beam, shown on the bottom left, is 46″ × 36″, with rms noise σ ∼ 1.9 mJy beam⁻¹. Contours are at −3, 3, 6, 12, 24 × σ. Top right: 144 MHz source-subtracted image of A1550 obtained applying Briggs −0.3 and tapering the visibilities to 30″. The beam is 36″ × 35″, with rms noise σ ∼ 0.14 mJy beam⁻¹. Contours are the same as above. Bottom left: 400 MHz source-subtracted image of A1550 obtained applying Briggs −0.3 and tapering the visibilities to 30″. The beam is 36″ × 26″, with rms noise σ ∼ 0.23 mJy beam⁻¹. Bottom right: 1.4 GHz source-subtracted image of A1550 obtained applying Briggs −0.3 and tapering the visibilities to to 30″. The beam is 32″ × 32″, with rms noise σ ∼ 23 μJy beam⁻¹.