Program: GN-2013B-Q-21

Recent observations suggested that the evolution of galaxies and supermassive black holes (SMBHs) are closely related, implying that the quasar evolution (powered by SMBHs) is a key factor to understand the galaxy formation. Interestingly, observations of quasars at $z<3$ show a so-called ``downsizing evolution", i.e., less-luminous quasars show the peak of a number density at lower redshifts than more luminous quasars. However this trend has not yet been confirmed at $z>3$ because the inferred number density of low-luminosity quasars is very controversial at $z¥sim4$, and there are no systematic surveys for low-luminosity quasars at $z¥sim5$. Here we propose a new spectroscopic campaign of photometric candidates of low-luminosity quasars at $z¥sim5$ for 6 $¥rm deg^2$ area in the CFHTLS wide fields. New constraints on the faint end of the quasar luminosity function at $z¥sim5$ will allow us to obtain a whole picture of the evolution of quasars and SMBHs, especially in terms of the downsizing scenario. Our observations will first examine whether or not there exists evidence for the downsizing evolution at $z>3$.