Top panel: the AGN duty cycle as a function of the galaxy stellar mass in six redshift bins. AGN with log L(2–10 keV)  >  43 are considered only. Bottom panel: the AGN duty cycle as a function of redshift for two galaxy stellar masses (log M_∗ = 11.25, 11.75 M_⊙). Filled circles and triangles are the previous determination of Brusa et al. (2009b) for the same masses. The black dashed (dotted) curve is the prediction of the Menci et al. (2006, 2008) SAM for log M_∗ = 11.25   M_⊙ (log M_∗ = 10 M_⊙).