Based on the radiation hydrodynamical model for black hole (BH) growth, together with the chemical evolution of an early-type host galaxy, we construct a co-evolution model of a QSO BH and the host galaxy. As a result, it is found that after a galactic wind epoch, the luminosity is shifted from the host-dominant phase to the AGN-dominant phase (QSO phase) in the timescale of a few 108yr. The former phase corresponds to the early stage of BH growth, and can be regarded as a ``proto-QSO'' phase. Also, by considering theoretical predictions for the observable properties in the proto-QSO phase, we conclude that radio galaxies may be possible candidates for proto-QSOs.
8th Asian-Pacific Regional Meeting, Volume II
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