Multiwavelength picture of the cluster A1758N (north at the top and east to the left). Optical density peaks detected from our analysis of the galaxy distribution (big blue circles; see Sect. 3.4) are superimposed on the SDSS r′-band image of the cluster region. Labels indicate the IDs of galaxies cited in the text. Thin red contour levels show the ICM distribution we derived from the X-ray Chandra archival image ID 2213 (photons in the energy range 0.3–7 keV; see David & Kempner 2004, for an extensive analysis of these X-ray data). From Giovannini et al. (2009) we also reproduce the radio contour levels of their VLA radio image at 1.4 GHz (thick black contours, HPBW = 45′′  ×  45′′) and highlight with arrows the positions of the radio halo (H, in the center) and the two peripheral radio relics (R1 and R2). The insert on the top left is a zoom on the region of the NAT radio galaxy 1330+507 (ID 105), with the radio contours taken from VLA high-resolution radio images presented by O’Dea & Owen (1985).