M 87 core/jet/lobe – intensity, spectral index and curvature: these images show 3-arcsec resolution maps of the central bright region of M 87 (core+jet and inner lobes). The quantities displayed are the intensity at 1.5 GHz (top left), the spectral index (top middle) and the spectral curvature (top right). The spectral index is near zero at the core, varies between  − 0.36 and  − 0.6 along the jet and out into the lobes. The spectral curvature is on average 0.5 which translates to  △ α = 0.2 across L-band. The plot at the bottom compares the resulting average spectrum (solid line) with that formed by imaging each spectral-window separately (dots). The dashed and dotted lines correspond to fixed values of spectral index (–0.43, –0.53, –0.63).