IR luminosity (derived for T_d = 35 K) versus redshift for the objects disussed here (arrows at z> 6.5) and for other samples. Colored small circles show individual galaxies detected with Herschel in various blank fields (red, Symeonidis et al. 2013; blue, Elbaz et al. 2011; green, Magdis et al. 2010). The observed behavior of L_IR with redshift for these galaxies is due to sensitivity limits of Herschel, as shown, e.g., by Elbaz et al. (2011). Large and small black circles show the lensed galaxies studied by Sklias et al. (2014) and Saintonge et al. (2013). The small dots show the predicted IR luminosity of LBGs from the sample studied by de Barros et al. (2014) and Schaerer & de Barros (in prep.). The blue line shows the IR luminosity of galaxies with a typical UV magnitude as predicted from the fit of A_UV with redshift by Burgarella et al. (2013).