Top left: heliocentric radial velocities in a 1.5 Mpc box centered on NGC 4756. The mean heliocentric radial velocity and the 3σ velocity dispersion of the group are identified (dashed lines). The second peak is due to A1631. Top right: B magnitude distribution of the group members. Bottom panels: spatial distribution of galaxies centered on NGC 4756 within 1.5 Mpc, and a zoom corresponding to the XMM-Newton field of view (right), superposed on the two-dimensional binned kernel-smoothed number-density contours. Filled red squares are group members listed in Grützbauch et al. (2005a). The dashed circle is centered on the center of mass of the group and identifies the virial radius.