while at lower redshifts $z=1-2$ the bimodal partition of the color distribution is appreciably enhanced by the effect of AGNs.

\[3.5\]

To perform a more quantitative comparison between the predicted and the observed bimodal properties of the galaxy population at intermediate and high redshifts, we compare in figs. 6 and 7 with the observational results from the Great Observatories Origins Deep Survey (GOODS) database. We show in fig. 6 the B-band luminosity functions of the red and blue components at different redshifts and compare them with the GOODS data (Salimbeni et al. 2006). According to the selection criterium discussed in Giallongo et al. (2005), in this plot we define the blue and the red population as those separated by the rest-frame color $U-V=\alpha(19.9+M_B)+(U-V)_0$ (Vega system), where the parameters $ \alpha$ and $(U-V)_0$ are given in the caption for the three redshift bins. At high redshifts ($z\gtrsim 2$) the model with no AGN feedbak substantially underestimates the number of red objects, while the model including the AGN energy injection produces a reasonable agreement at all redshifts for both the blue and the red population, although the long-standing problem of the overprediction of faint objects is still present in the model.

Note 