False-colour Z (blue), J (green), and Ks (red) image of a region corresponding to the galaxy group or cluster candidate. The red dashed circle delimits the six arcmin radius central area, the green lines indicate the two long-slit positions and the red squares show the five galaxies observed with F2. In the right panels, we zoomed in on the 58 galaxy candidates within the studied area. The length of each box side is 20 arcsec.