X-ray luminosity in the 0.2−2.3 keV band scaled by the SFR in the function of the sSFR for the full sample of normal galaxies divided into three redshift bins. The points size is proportional to the M_star. The solid black lines represent the observed fit of the sources, while the red dashed lines represent Lehmer et al. (2016) relation estimated at the mean value of the redshift for each bin. The shaded red region represents the 3σ dispersion.