Upper panel: Gas column density map of the main cluster in the NEWCLUSTER simulation at z = 1. The virial radius of the cluster is drawn with a grey circle. Numerous galaxies show gas tails within the early-stage cluster. Four galaxies chosen for representative illustration are marked with red circles. Bottom panel (left): Radial profile of the ram pressure exerted on galaxies (grey circles). The red dashed vertical line shows the virial radius. An evident decreasing trend of the magnitude of ram pressure can be seen. The ram pressures of the four representative galaxies are shown with the red circles. Bottom panel (right): Stellar density and gas column density distributions of the four galaxy samples. In each panel, the background density map is the surface brightness of the galaxy in r-band, and the contours show the column density distributions of cold gas. The red arrow indicates the direction of motion of the galaxy.