Two-dimensional kernel density map of galaxies on the red-sequence (red) in position space. Dots in gradient blues are galaxies detected in H I over the radial velocity range of the 3C 129 cluster (4000–8000 km s⁻¹). The displayed colour bar is the velocity range of the H I galaxies. The two white plus markers indicate the position of the X-ray emission over which the cluster is centred and the location near which the 3C129-A group lies and the orange stars are positions of the two radio sources, 3C129 and 3C129.1.