Left: 4′ × 4′z-band image of the cluster XDCP J1450.1+0904 – cl01 at z = 0.6417. X-ray contours are overlaid in blue, whereas red circles mark the member galaxies used in our kinematic analysis. The solid (dashed) black circle indicates a radius of 1′(0.5′) centered on the X-ray emission. Right: rest-frame velocity histogram of the cluster galaxies. The peculiar velocity (in km s^-1, bottom side) and the redshift values (top side) are reported in the panel with the estimated σ_v, its uncertainty, and the number of the clipped members contributing to the σ_v estimate. The solid curve is the best Gaussian fit of the distribution with variance equal to σ_v, whereas the dotted ones represent its ±1σ uncertainty.