CFHT/Megacam r-band image (north top and east left) of the galaxy cluster A780 with the contour levels of the XMM-Newton X-ray image superimposed (photons in the energy range 0.7−1.2 keV, De Grandi et al. 2016). Cluster members, as defined in Sect. 4, are highlighted by red circles (see Table 1). The numbers denote the galaxies discussed in the text: ID 47 (the BCG where the Hydra A radio source is located) and ID 97 (LEDA 87445).